Salt, acid generator, resist composition and method for producing resist pattern

ABSTRACT

Disclosed is a salt represented by formula (I): 
     
       
         
         
             
             
         
       
     
     wherein, in formula (I),
         Q 1  and Q 2  each independently represent a fluorine atom or the like,   R 1  and R 2  each independently represent a hydrogen atom or the like,   zi represents an integer of 0 to 6, and when zi is 2 or more, a plurality of R 1  and R 2  may be the same or different from each other,   X 1  represents *—CO—O—, *—O—CO— or the like (* represents a bonding site to C(R 1 )(R 2 ) or C(Q 1 )(Q 2 )),   L 1  represents a single bond or a divalent saturated hydrocarbon group having 1 to 28 carbon atoms or the like,   R 3  and R 4  each independently represent a cyclic hydrocarbon group having 3 to 18 carbon atoms which may have a substituent or the like, and   Z +  represents an organic cation.

TECHNICAL FIELD

The present invention relates to a salt for acid generator which is usedfor fine processing of a semiconductor, an acid generator including thesalt, a resist composition and a method for producing a resist pattern.

BACKGROUND ART

Patent Document 1 mentions a salt represented by the following formula,and a resist composition including the salt as an acid generator.

Patent Document 2 mentions a salt represented by the following formula,and a resist composition including the salt as an acid generator.

Patent Document 3 mentions a salt represented by the following formulaand a resist composition including the salt as an acid generator.

Patent Document 4 mentions a salt represented by the following formulaand a resist composition including the salt as an acid generator.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP 2007-161707 A

Patent Document 2: JP 2007-145824 A

Patent Document 3: JP 2010-039146 A

Patent Document 4: JP 2010-039476 A

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention provides a salt capable of producing a resistpattern with line edge roughness (LER) which is better than that of aresist pattern formed from the above-mentioned resist compositionincluding a salt.

Means for Solving the Problems

The present invention includes the following inventions.

[1] A salt represented by formula (I):

wherein, in formula (I),

Q¹ and Q² each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms,

R¹ and R² each independently represent a hydrogen atom, a fluorine atomor a perfluoroalkyl group having 1 to 6 carbon atoms,

zi represents an integer of 0 to 6, and when zi is 2 or more, aplurality of R¹ and R² may be the same or different form each other,

X¹ represents *—CO—O—, *—O—CO—, *—O—CO—O— or *—O— (* represents abonding site to C(R¹)(R²) or C(Q¹)(Q²)),

L¹ represents a single bond or a divalent saturated hydrocarbon grouphaving 1 to 28 carbon atoms, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—,

R³ and R⁴ each independently represent a cyclic hydrocarbon group having3 to 18 carbon atoms which may have a substituent, and —CH₂— included inthe cyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—,and

Z⁺ represents an organic cation.

[2] The salt according to [1], wherein X¹ represents *—CO—O—, *—O—CO— or*—O—CO—O— (* represents a bonding site to C(R¹)(R²) or C(Q¹)(Q²)).[3] The salt according to [1] or [2], wherein L¹ is a single bond, analkanediyl group (—CH₂— included in the alkanediyl group may be replacedby —O— or —CO—) or a group obtained by combining an alkanediyl group andan alicyclic saturated hydrocarbon group (—CH₂— included in thealkanediyl group may be replaced by —O— or —CO—, and —CH₂— included inthe alicyclic saturated hydrocarbon group may be replaced by —O—, —S—,—SO₂— or —CO—).[4] An acid generator comprising the salt according to any one of [1] to[3].[5] A resist composition comprising the acid generator according to [4]and a resin having an acid-labile group.[6] The resist composition according to [5], wherein the resin having anacid-labile group comprises at least one selected from the groupconsisting of a structural unit represented by formula (a1-1) and astructural unit represented by formula (a1-2):

wherein, in formula (a1-1) and formula (a1-2),

L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, and *represents a bond to —CO—.

R^(a4) and R^(a5) each independently represent a hydrogen atom or amethyl group,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, or a group obtained by combining these groups,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

[7] The resist composition according to [5] or [6], further comprising asalt generating an acid having an acidity lower than that of an acidgenerated from the acid generator.[8] The resist composition according to any one of [5] to [7] furthercomprising a resin including a structural unit having a fluorine atom.[9] A method for producing a resist pattern, which comprises:

(1) a step of applying the resist composition according to any one of[5] to [8] on a substrate,

(2) a step of drying the applied composition to form a compositionlayer,

(3) a step of exposing the composition layer,

(4) a step of heating the exposed composition layer, and

(5) a step of developing the heated composition layer.

Effects of the Invention

It is possible to produce a resist pattern with satisfactory line edgeroughness (LER) by using a resist composition using a salt of thepresent invention.

MODE FOR CARRYING OUT THE INVENTION

As used herein, “(meth)acrylic monomer” means at least one selected fromthe group consisting of a monomer having a structure of “CH₂═CH—CO—” anda monomer having a structure of “CH₂═C(CH₃)—CO—”. Similarly,“(meth)acrylate” and “(meth)acrylic acid” each mean “at least oneselected from the group consisting of acrylate and methacrylate” and “atleast one selected from the group consisting of acrylic acid andmethacrylic acid”. When a structural unit having “CH₂═C(CH₃)—CO—” or“CH₂═CH—CO—” is exemplified, a structural unit having both groups shallbe similarly exemplified. In groups mentioned in the presentdescription, regarding groups capable of having both a linear structureand a branched structure, they may have either the linear or branchedstructure. “Combined group” means a group in which two or moreexemplified groups are bonded, and valences of those groups may beappropriately changed depending on a bonding form. When stereoisomersexist, all stereoisomers are included.

As used herein, “solid component of resist composition” means the totalof components excluding the below-mentioned solvent (E) from the totalamount of the resist composition.

<Salt Represented by Formula (I)>

The present invention relates to a salt represented by formula (I)(hereinafter sometimes referred to as “salt (I)”).

Of the salt (I), the side having negative charge is sometimes referredto as “anion (I)”, and the side having positive charge is sometimesreferred to as “cation (I)”.

Examples of the perfluoroalkyl group of Q¹, Q², R¹ and R² in formula (1)include a trifluoromethyl group, a perfluoroethyl group, aperfluoropropyl group, a perfluoroisopropyl group, a perfluorobutylgroup, a perfluorosec-butyl group, a perfluorotert-butyl group, aperfluoropentyl group, a perfluorohexyl group and the like.

Preferably, Q¹ and Q² are each independently a trifluoromethyl group ora fluorine atom, and more preferably a fluorine atom.

Preferably, R¹ and R² are each independently a hydrogen atom or afluorine atom.

zi is preferably 0 or 1.

X¹ is preferably *—CO—O—, *—O—CO— or *—O—CO—O— (* represents a bond toC(R¹)(R²) or C(Q¹)(Q²)).

Examples of the divalent saturated hydrocarbon group represented by L¹include an alkanediyl group and a monocyclic or polycyclic divalentalicyclic saturated hydrocarbon group, and the divalent saturatedhydrocarbon group may be a group obtained by combining two or more ofthese groups (e.g., divalent hydrocarbon group formed from an alicyclichydrocarbon group and an alkanediyl group and the like).

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, atetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, ahexadecane-1,16-diyl group and a heptadecane-1,17-diyl group;

branched alkanediyl groups such as an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups such as acyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, acyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group; and

polycyclic divalent alicyclic saturated hydrocarbon groups such as anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, anadamantane-1,5-diyl group and an adamantane-2,6-diyl group.

—CH₂— included in the divalent saturated hydrocarbon group having 1 to28 carbon atoms of L may be replaced by —O—, —S—, —SO₂— or —CO—.

When —CH₂— included in the divalent saturated hydrocarbon group having 1to 28 carbon atoms represented by L¹ is replaced by —O—, —S—, —SO₂— or—CO—, the number of carbon atoms before replacement is regarded as thenumber of carbon atoms of the hydrocarbon group.

Examples of the group in which —CH₂— included in L is replaced by —O— or—CO— include a hydroxy group, an alkoxy group, an alkoxycarbonyl group,an alkylcarbonyl group, an alkylcarbonyloxy group, a carboxy group, analkanediyloxy group, an alkanediyloxycarbonyl group, analkanediylcarbonyl group, an alkanediylcarbonyloxy group and the like.

Examples of an alkoxy group, an alkoxycarbonyl group, an alkylcarbonylgroup and an alkylcarbonyloxy group include those which are the same asthe substituent mentioned below in R³ and R⁴.

L¹ may be a divalent saturated hydrocarbon group having 1 to 28 carbonatoms (—CH₂— included in the saturated hydrocarbon group may be replacedby —O—, —S—, —SO₂— or —CO—), and is preferably a single bond, analkanediyl group having 1 to 4 carbon atoms (—CH₂— included in thealkanediyl group may be replaced by —O— or —CO—), or a group obtained bycombining an alkanediyl group having 1 to 4 carbon atoms and analicyclic saturated hydrocarbon group having 3 to 18 carbon atoms (—CH₂—included in the alkanediyl group may be replaced by —O— or —CO—, and—CH₂— included in the alicyclic saturated hydrocarbon group may bereplaced by —O—, —S—, —SO₂— or —CO—), more preferably a single bond, analkanediyl group having 1 to 4 carbon atoms, or a group obtained bycombining an alkanediyl group having 1 to 4 carbon atoms and analicyclic saturated hydrocarbon group having 3 to 18 carbon atoms (—CH₂—included in the alkanediyl group may be replaced by —O— or —CO—), andstill more preferably, a single bond, an alkanediyl group having 1 to 4carbon atoms, or a group obtained by combining an alkanediyl grouphaving 1 to 4 carbon atoms and an adamantanediyl group (—CH₂— includedin the alkanediyl group may be replaced by —O— or —CO—).

Examples of the cyclic hydrocarbon group having 3 to 18 carbon atoms ofR³ and R⁴ include a monocyclic or polycyclic alicyclic hydrocarbon grouphaving 3 to 18 carbon atoms and an aromatic hydrocarbon group having 6to 18 carbon atoms.

Examples of the monocyclic alicyclic hydrocarbon group includemonocyclic cycloalkyl groups such as a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, acyclooctyl group, a cyclononyl group, a cyclodecyl group, a cyclododecylgroup and the like.

Examples of the polycyclic alicyclic hydrocarbon group include adecahydronaphthyl group, an adamantyl group, a norbornyl group and thelike.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, a biphenyl group, an anthryl group, aphenanthryl group and a binaphthyl group.

Examples of the substituent which may be possessed by the cyclichydrocarbon group of R³ and R⁴ include a halogen atom, a cyano group, analkyl group having 1 to 12 carbon atoms (—CH₂— included in the alkylgroup may be replaced by —O—, —S—, —CO— or —SO₂—) and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alkyl group having 1 to 12 carbon atoms include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, a hexylgroup, an octyl group, a nonyl group and the like.

When —CH₂— included in the alkyl group as the substituent is replaced by—O— or —CO—, the number of carbon atoms before replacement is regardedas the total number of carbon atoms of the alkyl group. Examples thereofinclude a hydroxy group (group in which —CH₂— included in the methylgroup is replaced by —O—), a carboxy group (group in which —CH₂—CH₂—included in the ethyl group is replaced by —O—CO—), an alkoxy grouphaving 1 to 11 carbon atoms (group in which —CH₂— included in the alkylgroup having 2 to 12 carbon atoms is replaced by —O—), an alkoxycarbonylgroup having 2 to 11 carbon atoms (group in which —CH₂—CH₂— included inthe alkyl group having 3 to 12 carbon atoms is replaced by —O—CO—), analkylcarbonyl group having 2 to 12 carbon atoms (group in which —CH₂—included in the alkyl group having 2 to 12 carbon atoms is replaced by—CO—), an alkylcarbonyloxy group having 2 to 11 carbon atoms (group inwhich —CH₂—CH₂— included in the alkyl group having 3 to 12 carbon atomsis replaced by —CO—O—) and the like.

Examples of the alkoxy group having 1 to 11 carbon atoms include amethoxy group, an ethoxy group, a propoxy group, a butoxy group, apentyloxy group, a hexyloxy group, an octyloxy group, a 2-ethylhexyloxygroup, a nonyloxy group, a decyloxy group, a undecyloxy group and thelike.

The alkoxycarbonyl group, the alkylcarbonyl group and thealkylcarbonyloxy group represent a group in which a carbonyl group or acarbonyloxy group is bonded to the above-mentioned alkyl group or alkoxygroup.

Examples of the alkoxycarbonyl group having 2 to 11 carbon atoms includea methoxycarbonyl group, an ethoxycarbonyl group, a butoxycarbonyl groupand the like, examples of the alkylcarbonyl group having 2 to 12 carbonatoms include an acetyl group, a propionyl group and a butyryl group,and examples of the alkylcarbonyloxy group having 2 to 11 carbon atomsinclude an acetyloxy group, a propionyloxy group, a butyryloxy group andthe like.

The cyclic hydrocarbon group having 3 to 18 carbon atoms may have onesubstituent or a plurality of substituents.

The cyclic hydrocarbon group having 3 to 18 carbon atoms represented byR³ and R⁴ may have one substituent, or a plurality of substituents whichare the same or different.

—CH₂— included in the cyclic hydrocarbon group having 3 to 18 carbonatoms of R³ and R⁴ may be replaced by —O—, —S—, —CO— or —SO₂—.

When the divalent alicyclic hydrocarbon group having 3 to 18 carbonatoms represented by A¹ has a substituent or —CH₂— included in thealicyclic hydrocarbon group is replaced by —O—, —S—, —CO— or —SO₂—, thenumber of carbon atoms before replacement is regarded as the number ofcarbon atoms of the hydrocarbon group.

The cyclic hydrocarbon group having 3 to 18 carbon atoms which may havea substituent represented by R³ and R⁴ is preferably an alicyclichydrocarbon group having 3 to 18 carbon atoms which may have one or moresubstitutes selected from the group consisting of an alkyl group having1 to 8 carbon atoms (—CH₂— included in the alkyl group may be replacedby —O—, —S—, —CO— or —SO₂—) and a fluorine atom or an aromatichydrocarbon group having 6 to 18 carbon atoms which may have one or moresubstitutes selected from the group consisting of an alkyl group having1 to 8 carbon atoms (—CH₂— included in the alkyl group may be replacedby —O—, —S—, —CO— or —SO₂—) and a fluorine atom, and more preferably amonocyclic alicyclic hydrocarbon group having 5 to 8 carbon atoms whichmay have an alkyl group having 1 to 4 carbon atoms, an alkoxy grouphaving 1 to 3 carbon atoms, a hydroxy group or a fluorine atom or aphenyl group which may have an alkyl group having 1 to 4 carbon atoms,an alkoxy group having 1 to 3 carbon atoms, a hydroxy group or afluorine atom.

Examples of the anion (I) include the following anions. Of these, anionsrepresented by formula (Ia-1) to formula (Ia-3), formula (Ia-9), formula(Ia-11) and formula (Ia-13) to formula (Ia-18) are preferable.

Examples of the organic cation of Z* include an organic onium cation, anorganic sulfonium cation, an organic iodonium cation, an organicammonium cation, a benzothiazolium cation and an organic phosphoniumcation and the like. Of these organic cations, an organic sulfoniumcation and an organic iodonium cation are preferable, and anarylsulfonium cation is more preferable. Specific examples thereofinclude a cation represented by any one of formula (b2-1) to formula(b2-4) (hereinafter sometimes referred to as “cation (b2-1)” accordingto the number of formula.

In formula (b2-1) to formula (b2-4),

R^(b4) to R^(b6) each independently represent a chain hydrocarbon grouphaving 1 to 30 carbon atoms, an alicyclic hydrocarbon group having 3 to36 carbon atoms or an aromatic hydrocarbon group having 6 to 36 carbonatoms, a hydrogen atom included in the chain hydrocarbon group may besubstituted with a hydroxy group, an alkoxy group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 12 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the alicyclic hydrocarbon group may be substituted with ahalogen atom, an aliphatic hydrocarbon group having 1 to 18 carbonatoms, an alkylcarbonyl group having 2 to 4 carbon atoms or aglycidyloxy group, and a hydrogen atom included in the aromatichydrocarbon group may be substituted with a halogen atom, a hydroxygroup or an alkoxy group having 1 to 12 carbon atoms,

R^(b4) and R^(b5) may be bonded to each other to form a ring togetherwith sulfur atoms to which R^(b4) and R^(b5) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b7) and R^(b8) each independently represent a hydroxy group, analiphatic hydrocarbon group having 1 to 12 carbon atoms or an alkoxygroup having 1 to 12 carbon atoms,

m2 and n2 each independently represent an integer of 0 to 5,

when m2 is 2 or more, a plurality of R^(b7) may be the same ordifferent, and when n2 is 2 or more, a plurality of R^(b8) may be thesame or different,

R^(b9) and R^(b10) each independently represent a chain hydrocarbongroup having 1 to 36 carbon atoms or an alicyclic hydrocarbon grouphaving 3 to 36 carbon atoms,

R^(b9) and R^(b10) may be bonded to each other to form a ring togetherwith sulfur atoms to which R^(b9) and R^(b10) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b11) represents a hydrogen atom, a chain hydrocarbon group having 1to 36 carbon atoms, an alicyclic hydrocarbon group having 3 to 36 carbonatoms or an aromatic hydrocarbon group having 6 to 18 carbon atoms,

R^(b12) represents a chain hydrocarbon group having 1 to 12 carbonatoms, an alicyclic hydrocarbon group having 3 to 18 carbon atoms or anaromatic hydrocarbon group having 6 to 18 carbon atoms, a hydrogen atomincluded in the chain hydrocarbon may be substituted with an aromatichydrocarbon group having 6 to 18 carbon atoms, and a hydrogen atomincluded in the aromatic hydrocarbon group may be substituted with analkoxy group having 1 to 12 carbon atoms or an alkylcarbonyloxy grouphaving 1 to 12 carbon atoms,

R^(b11) and R^(b12) may be bonded to each other to form a ring,including —CH—CO— to which R^(b11) and R^(b12) are bonded, and —CH₂—included in the ring may be replaced by —O—, —S— or —CO—,

R^(b13) to R^(b18) each independently represent a hydroxy group, analiphatic hydrocarbon group having 1 to 12 carbon atoms or an alkoxygroup having 1 to 12 carbon atoms,

L^(b31) represents a sulfur atom or an oxygen atom,

o2, p2, s2 and t2 each independently represent an integer of 0 to 5,

q2 and r2 each independently represent an integer of 0 to 4,

u2 represents 0 or 1, and

when o2 is 2 or more, a plurality of R^(b13) are the same or different,when p2 is 2 or more, a plurality of R^(b14) are the same or different,when q2 is 2 or more, a plurality of R^(b15) are the same or different,when r2 is 2 or more, a plurality of R^(b16) are the same or different,when s2 is 2 or more, a plurality of R^(b17) are the same or different,and when t2 is 2 or more, a plurality of R^(b18) are the same ordifferent.

The aliphatic hydrocarbon group represents a chain hydrocarbon group andan alicyclic hydrocarbon group.

Examples of the chain hydrocarbon group include alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, an octyl group and a 2-ethylhexyl group. Particularly, thechain hydrocarbon group of R^(b9) to R^(b12) preferably has 1 to 12carbon atoms.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic,and examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctylgroup and a cyclodecyl group. Examples of the polycyclic alicyclichydrocarbon group include a decahydronaphthyl group, an adamantyl group,a norbornyl group and the following groups.

Particularly, the alicyclic hydrocarbon group of R^(b9) to R^(b12)preferably has 3 to 18 carbon atoms, and more preferably 4 to 12 carbonatoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom issubstituted with an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, a2-methyladamantan-2-yl group, a 2-ethyladamantan-2-yl group, a2-isopropyladamantan-2-yl group, a methylnorbornyl group, an isobornylgroup and the like. In the alicyclic hydrocarbon group in which ahydrogen atom is substituted with an aliphatic hydrocarbon group, thetotal number of carbon atoms of the alicyclic hydrocarbon group and thealiphatic hydrocarbon group is preferably 20 or less.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a biphenyl group, a naphthyl group and a phenanthrylgroup. The aromatic hydrocarbon group may have a chain hydrocarbon groupor an alicyclic hydrocarbon group, and examples thereof include anaromatic hydrocarbon group having a chain hydrocarbon group (a tolylgroup, a xylyl group, a cumenyl group, a mesityl group, a p-ethylphenylgroup, a p-tert-butylphenyl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group, etc.) and an aromatic hydrocarbon grouphaving an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, ap-adamantylphenyl group, etc.). When the aromatic hydrocarbon group hasa chain hydrocarbon group or an alicyclic hydrocarbon group, a chainhydrocarbon group having 1 to 18 carbon atoms and an alicyclichydrocarbon group having 3 to 18 carbon atoms are preferable.

Examples of the aromatic hydrocarbon group in which a hydrogen atom issubstituted with an alkoxy group include a p-methoxyphenyl group and thelike.

Examples of the chain hydrocarbon group in which a hydrogen atom issubstituted with an aromatic hydrocarbon group include aralkyl groupssuch as a benzyl group, a phenethyl group, a phenylpropyl group, atrityl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alkylcarbonyloxy group include a methylcarbonyloxygroup, an ethylcarbonyloxy group, a propylcarbonyloxy group, anisopropylcarbonyloxy group, a butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethylhexylcarbonyloxy group.

The ring formed by bonding R^(b4) and R^(b5) each other, together withsulfur atoms to which R^(b4) and R^(b5) are bonded, may be a monocyclic,polycyclic, aromatic, nonaromatic, saturated or unsaturated ring. Thisring includes a ring having 3 to 18 carbon atoms and is preferably aring having 4 to 18 carbon atoms. The ring containing a sulfur atomincludes a 3-membered to 12-membered ring and is preferably a 3-memberedto 7-membered ring and includes, for example, the following rings andthe like. * represents a bonding site.

The ring formed by combining R^(b9) and R^(b10) together may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. The ring includes, forexample, a thiolan-1-ium ring (tetrahydrothiophenium ring), athian-1-ium ring, a 1,4-oxathian-4-ium ring and the like.

The ring formed by combining R^(b11) and R^(b12) together may be amonocyclic, polycyclic, aromatic, nonaromatic, saturated or unsaturatedring. This ring includes a 3-membered to 12-membered ring and ispreferably a 3-membered to 7-membered ring. Examples thereof include anoxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, anoxoadamantane ring and the like.

Of cation (b2-1) to cation (b2-4), a cation (b2-1) is preferable.

Examples of the cation (b2-1) include the following cations.

Examples of the cation (b2-2) include the following cations.

Examples of the cation (b2-3) include the following cations.

Examples of the cation (b2-4) include the following cations.

Examples of the salt (I) include salts shown in Table 1 to Table 6. Forexample, in Table 1, the salt (I-1) is a salt composed of an anionrepresented by formula (Ia-1) and a cation represented by formula(b2-c-1) and is the following salt.

TABLE 1 Salt (I) Anion (I) Cation (I) (I-1) (Ia-1) (b2-c-1) (I-2) (Ia-2)(b2-c-1) (I-3) (Ia-3) (b2-c-1) (I-4) (Ia-4) (b2-c-1) (I-5) (Ia-5)(b2-c-1) (I-6) (Ia-6) (b2-c-1) (I-7) (Ia-7) (b2-c-1) (I-8) (Ia-8)(b2-c-1) (I-9) (Ia-9) (b2-c-1) (I-10) (Ia-10) (b2-c-1) (I-11) (Ia-11)(b2-c-1) (I-12) (Ia-12) (b2-c-1) (I-13) (Ia-13) (b2-c-1) (I-14) (Ia-14)(b2-c-1) (I-15) (Ia-15) (b2-c-1) (I-16) (Ia-16) (b2-c-1) (I-17) (Ia-17)(b2-c-1) (I-18) (Ia-18) (b2-c-1) (I-19) (Ia-19) (b2-c-1) (I-20) (Ia-20)(b2-c-1) (I-21) (Ia-1) (b2-c-10) (I-22) (Ia-2) (b2-c-10) (I-23) (Ia-3)(b2-c-10) (I-24) (Ia-4) (b2-c-10) (I-25) (Ia-5) (b2-c-10) (I-26) (Ia-6)(b2-c-10) (I-27) (Ia-7) (b2-c-10) (I-28) (Ia-8) (b2-c-10) (I-29) (Ia-9)(b2-c-10) (I-30) (Ia-10) (b2-c-10) (I-31) (Ia-11) (b2-c-10) (I-32)(Ia-12) (b2-c-10) (I-33) (Ia-13) (b2-c-10) (I-34) (Ia-14) (b2-c-10)(I-35) (Ia-15) (b2-c-10)

TABLE 2 Salt (I) Anion (I) Cation (I) (I-36) (Ia-16) (b2-c-10) (I-37)(Ia-17) (b2-c-10) (I-38) (Ia-18) (b2-c-10) (I-39) (Ia-19) (b2-c-10)(I-40) (Ia-20) (b2-c-10) (I-41) (Ia-1) (b2-c-12) (I-42) (Ia-2) (b2-c-12)(I-43) (Ia-3) (b2-c-12) (I-44) (Ia-4) (b2-c-12) (I-45) (Ia-5) (b2-c-12)(I-46) (Ia-6) (b2-c-12) (I-47) (Ia-7) (b2-c-12) (I-48) (Ia-8) (b2-c-12)(I-49) (Ia-9) (b2-c-12) (I-50) (Ia-10) (b2-c-12) (I-51) (Ia-11)(b2-c-12) (I-52) (Ia-12) (b2-c-12) (I-53) (Ia-13) (b2-c-12) (I-54)(Ia-14) (b2-c-12) (I-55) (Ia-15) (b2-c-12) (I-56) (Ia-16) (b2-c-12)(I-57) (Ia-17) (b2-c-12) (I-58) (Ia-18) (b2-c-12) (I-59) (Ia-19)(b2-c-12) (I-60) (Ia-20) (b2-c-12) (I-61) (Ia-1) (b2-c-14) (I-62) (Ia-2)(b2-c-14) (I-63) (Ia-3) (b2-c-14) (I-64) (Ia-4) (b2-c-14) (I-65) (Ia-5)(b2-c-14) (I-66) (Ia-6) (b2-c-14) (I-67) (Ia-7) (b2-c-14) (I-68) (Ia-8)(b2-c-14) (I-69) (Ia-9) (b2-c-14) (I-70) (Ia-10) (b2-c-14)

TABLE 3 Salt (I) Anion (I) Cation (I) (I-71) (Ia-11) (b2-c-14) (I-72)(Ia-12) (b2-c-14) (I-73) (Ia-13) (b2-c-14) (I-74) (Ia-14) (b2-c-14)(I-75) (Ia-15) (b2-c-14) (I-76) (Ia-16) (b2-c-14) (I-77) (Ia-17)(b2-c-14) (I-78) (Ia-18) (b2-c-14) (I-79) (Ia-19) (b2-c-14) (I-80)(Ia-20) (b2-c-14) (I-81) (Ia-1) (b2-c-18) (I-82) (Ia-2) (b2-c-18) (I-83)(Ia-3) (b2-c-18) (I-84) (Ia-4) (b2-c-18) (I-85) (Ia-5) (b2-c-18) (I-86)(Ia-6) (b2-c-18) (I-87) (Ia-7) (b2-c-18) (I-88) (Ia-8) (b2-c-18) (I-89)(Ia-9) (b2-c-18) (I-90) (Ia-10) (b2-c-18) (I-91) (Ia-11) (b2-c-18)(I-92) (Ia-12) (b2-c-18) (I-93) (Ia-13) (b2-c-18) (I-94) (Ia-14)(b2-c-18) (I-95) (Ia-15) (b2-c-18) (I-96) (Ia-16) (b2-c-18) (I-97)(Ia-17) (b2-c-18) (I-98) (Ia-18) (b2-c-18) (I-99) (Ia-19) (b2-c-18)(I-100) (Ia-20) (b2-c-18) (I-101) (Ia-1) (b2-c-18) (I-102) (Ia-2)(b2-c-19) (I-103) (Ia-3) (b2-c-19) (I-104) (Ia-4) (b2-c-19) (I-105)(Ia-5) (b2-c-19)

TABLE 4 Salt (I) Anion (I) Cation (I) (I-106) (Ia-6) (b2-c-19) (I-107)(Ia-7) (b2-c-19) (I-108) (Ia-8) (b2-c-19) (I-109) (Ia-9) (b2-c-19)(I-110) (Ia-10) (b2-c-19) (I-111) (Ia-11) (b2-c-19) (I-112) (Ia-12)(b2-c-19) (I-113) (Ia-13) (b2-c-19) (I-114) (Ia-14) (b2-c-19) (I-115)(Ia-15) (b2-c-19) (I-116) (Ia-16) (b2-c-19) (I-117) (Ia-17) (b2-c-19)(I-118) (Ia-18) (b2-c-19) (I-119) (Ia-19) (b2-c-19) (I-120) (Ia-20)(b2-c-19) (I-121) (Ia-1) (b2-c-20) (I-122) (Ia-2) (b2-c-20) (I-123)(Ia-3) (b2-c-20) (I-124) (Ia-4) (b2-c-20) (I-125) (Ia-5) (b2-c-20)(I-126) (Ia-6) (b2-c-20) (I-127) (Ia-7) (b2-c-20) (I-128) (Ia-8)(b2-c-20) (I-129) (Ia-9) (b2-c-20) (I-130) (Ia-10) (b2-c-20) (I-131)(Ia-11) (b2-c-20) (I-132) (Ia-12) (b2-c-20) (I-133) (Ia-13) (b2-c-20)(I-134) (Ia-14) (b2-c-20) (I-135) (Ia-15) (b2-c-20) (I-136) (Ia-16)(b2-c-20) (I-137) (Ia-17) (b2-c-20) (I-138) (Ia-18) (b2-c-20) (I-139)(Ia-19) (b2-c-20) (I-140) (Ia-20) (b2-c-20)

TABLE 5 Salt (I) Anion (I) Cation (I) (I-141) (Ia-1) (b2-c-27) (I-142)(Ia-2) (b2-c-27) (I-143) (Ia-3) (b2-c-27) (I-144) (Ia-4) (b2-c-27)(I-145) (Ia-5) (b2-c-27) (I-146) (Ia-6) (b2-c-27) (I-147) (Ia-7)(b2-c-27) (I-148) (Ia-8) (b2-c-27) (I-149) (Ia-9) (b2-c-27) (I-150)(Ia-10) (b2-c-27) (I-151) (Ia-11) (b2-c-27) (I-152) (Ia-12) (b2-c-27)(I-153) (Ia-13) (b2-c-27) (I-154) (Ia-14) (b2-c-27) (I-155) (Ia-15)(b2-c-27) (I-156) (Ia-16) (b2-c-27) (I-157) (Ia-17) (b2-c-27) (I-158)(Ia-18) (b2-c-27) (I-159) (Ia-19) (b2-c-27) (I-160) (Ia-20) (b2-c-27)(I-161) (Ia-1) (b2-c-30) (I-162) (Ia-2) (b2-c-30) (I-163) (Ia-3)(b2-c-30) (I-164) (Ia-4) (b2-c-30) (I-165) (Ia-5) (b2-c-30) (I-166)(Ia-6) (b2-c-30) (I-167) (Ia-7) (b2-c-30) (I-168) (Ia-8) (b2-c-30)(I-169) (Ia-9) (b2-c-30) (I-170) (Ia-10) (b2-c-30) (I-171) (Ia-11)(b2-c-30) (I-172) (Ia-12) (b2-c-30) (I-173) (Ia-13) (b2-c-30) (I-174)(Ia-14) (b2-c-30) (I-175) (Ia-15) (b2-c-30)

TABLE 6 Salt (I) Anion (I) Cation (I) (I-176) (Ia-16) (b2-c-30) (I-177)(Ia-17) (b2-c-30) (I-178) (Ia-18) (b2-c-30) (I-179) (Ia-19) (b2-c-30)(I-180) (Ia-20) (b2-c-30) (I-181) (Ia-1) (b2-c-31) (I-182) (Ia-2)(b2-c-31) (I-183) (Ia-3) (b2-c-31) (I-184) (Ia-4) (b2-c-31) (I-185)(Ia-5) (b2-c-31) (I-186) (Ia-6) (b2-c-31) (I-187) (Ia-7) (b2-c-31)(I-188) (Ia-8) (b2-c-31) (I-189) (Ia-9) (b2-c-31) (I-190) (Ia-10)(b2-c-31) (I-191) (Ia-11) (b2-c-31) (I-192) (Ia-12) (b2-c-31) (I-193)(Ia-13) (b2-c-31) (I-194) (Ia-14) (b2-c-31) (I-195) (Ia-15) (b2-c-31)(I-196) (Ia-16) (b2-c-31) (I-197) (Ia-17) (b2-c-31) (I-198) (Ia-18)(b2-c-31) (I-199) (Ia-19) (b2-c-1) (I-200) (Ia-20) (b2-c-1)

Of these salts, the salt (I) preferably includes salt (I-1) to salt(I-3), salt (I-9), salt (I-11), salt (I-13) to salt (I-18), salt (I-21)to salt (I-23), salt (I-29), salt (1-31), salt (I-33) to salt (I-38),salt (I-41) to salt (I-43), salt (I-49), salt (I-51), salt (I-53) tosalt (I-58), salt (I-61) to salt (I-63), salt (I-69), salt (I-71), salt(1-73) to salt (I-78), salt (I-81) to salt (I-83), salt (I-89), salt(I-91), salt (I-93) to salt (I-98), salt (I-101) to salt (I-103), salt(I-109), salt (I-111), salt (I-113) to salt (I-118), salt (I-121) tosalt (I-123), salt (I-129), salt (I-131), salt (I-133) to salt (I-138),salt (I-141) to salt (I-143), salt (I-149), salt (I-151), salt (I-153)to salt (I-158), salt (I-161) to salt (I-163), salt (I-169), salt(I-171), salt (I-173) to salt (I-178), salt (I-181) to salt (I-183),salt (I-189), salt (I-191) and salt (I-193) to salt (I-198).

<Method for Producing Salt (I)>

A salt in which X¹ is *—CO—O— in the salt (I) (salt represented byformula (I1)) can be produced, for example, by reacting a saltrepresented by formula (I1-a) with carbonyldiimidazole in a solvent,followed by further reaction with a compound represented by formula(I1-b):

wherein all symbols are the same as defined above.

Examples of the solvent in this reaction include chloroform,acetonitrile and the like.

The reaction temperature is usually 5° C. to 80° C., and the reactiontime is usually 0.5 hour to 24 hours.

The salt represented by formula (I1-a) includes, for example, a saltrepresented by the following and can be produced by the method mentionedin JP 2008-127367 A.

The compound represented by formula (I1-b) includes compoundsrepresented by the following formulas and is easily available on themarket.

A salt in which X¹ is *—O—CO—O— in the salt (I) (salt represented byformula (I2)) can be produced, for example, by reacting a saltrepresented by formula (I2-a) with carbonyldiimidazole in a solvent,followed by a reaction with a compound represented by formula (I1-b).

The salt represented by formula (I2) can also be produced, for example,by reacting a compound represented by formula (I1-b) withcarbonyldiimidazole in a solvent, followed by a reaction with a saltrepresented by formula (I2-a):

wherein all symbols are the same as defined above.

Examples of the solvent in this reaction include chloroform,acetonitrile and the like.

The reaction temperature is usually 5° C. to 80° C., and the reactiontime is usually 0.5 hour to 24 hours.

The salt represented by formula (I2-a) includes, for example, a saltrepresented by the following, and can be produced by the methodmentioned in JP 2012-193170 A.

A salt in which X¹ is *—O—CO— in the salt (I) (salt represented byformula (I3)) can be produced, for example, by reacting a compoundrepresented by formula (I3-b) with carbonyldiimidazole in a solvent,followed by a reaction with a salt represented by formula (I2-a):

wherein all symbols are the same as defined above.

Examples of the solvent in this reaction include chloroform,acetonitrile and the like.

The reaction temperature is usually 5° C. to 80° C., and the reactiontime is usually 0.5 hour to 24 hours.

The compound represented by formula (I3-b) includes compoundsrepresented by the following formulas, which are easily available on themarket.

A slat in which X¹ is —O— in the salt (I) (salt represented by formula(I4)) can be obtained by reacting a salt represented by formula (I2-a)with a compound represented by formula (I1-b) in the presence of a basein a solvent:

wherein all symbols are the same as defined above.

Examples of the base in this reaction include potassium hydroxide andthe like.

Examples of the solvent in this reaction include acetonitrile and thelike.

The reaction temperature is usually 5° C. to 80° C., and the reactiontime is usually 0.5 hour to 24 hours.

It is possible to produce a salt in which L¹ is*-L^(I4)-Ad-L^(I5)-O—CO—O-L^(I6) in the salt (I) (salt represented byformula (I5)) (L^(I4), L^(I5) and L^(I6) each independently represent asingle bond or an alkanediyl group having 1 to 6 carbon atoms, at leastone of L^(I4), L^(I5) and L^(I6) represents an alkanediyl group having 1to 6 carbon atoms, Ad represents an adamantanediyl group, and *represents a bonding site to X¹), for example, by reacting a saltrepresented by formula (I5-a) with a compound represented by formula(I5-b) in a solvent:

wherein all symbols are the same as defined above.

The reaction temperature is usually 5° C. to 80° C., and the reactiontime is usually 0.5 hour to 24 hours.

Examples of the solvent in this reaction include chloroform,acetonitrile and the like.

The salt represented by formula (I5-a) includes, for example, saltsrepresented by the following, and can be produced by the methodmentioned in JP 2012-72109 A.

The compound represented by formula (I5-b) includes, for example, acompound represented by formula (I1-b).

<Acid Generator>

The acid generator of the present invention is an acid generatorincluding the salt (I). The salt (I) may be used alone, or two or morethereof may be used in combination.

The acid generator of the present invention may include, in addition tothe salt (I), an acid generator known in the resist field (hereinaftersometimes referred to as “acid generator (B)”). The acid generator (B)may be used alone, or two or more acid generators may be used incombination.

Either nonionic or ionic acid generator may be used as the acidgenerator (B). Examples of the nonionic acid generator include sulfonateesters (e.g., 2-nitrobenzyl ester, aromatic sulfonate, oxime sulfonate,N-sulfonyloxyimide, sulfonyloxyketone, diazonaphthoquinone 4-sulfonate),sulfones (e.g., disulfone, ketosulfone, sulfonyldiazomethane) and thelike. Typical examples of the ionic acid generator include onium saltscontaining an onium cation (e.g., diazonium salt, phosphonium salt,sulfonium salt, iodonium salt). Examples of the anion of the onium saltinclude sulfonic acid anion, sulfonylimide anion, sulfonylmethide anionand the like.

Specific examples of the acid generator (B) include compounds generatingan acid upon exposure to radiation mentioned in JP 63-26653 A, JP55-164824 A, JP 62-69263 A, JP 63-146038 A, JP 63-163452 A, JP 62-153853A, JP 63-146029 A, U.S. Pat. Nos. 3,779,778, 3,849,137, DE Patent No.3914407 and EP Patent No. 126,712. Compounds produced by a known methodmay also be used. Two or more acid generators (B) may also be used incombination.

The acid generator (B) is preferably a fluorine-containing acidgenerator, and more preferably a salt represented by formula (B1)(hereinafter sometimes referred to as “acid generator (B1)”, excludingthe salt (I)):

wherein, in formula (B1),

Q^(b1) and Q^(b2) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms,

L^(b1) represents a divalent saturated hydrocarbon group having 1 to 24carbon atoms, —CH₂— included in the divalent saturated hydrocarbon groupmay be replaced by —O— or —CO—, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group,

Y represents a methyl group which may have a substituent or an alicyclichydrocarbon group having 3 to 18 carbon atoms which may have asubstituent, and —CH₂— included in the alicyclic hydrocarbon group maybe replaced by —O—, —S(O)₂— or —CO—, and

Z1⁺ represents an organic cation.

Examples of the perfluoroalkyl group represented by Q^(b1) and Q^(b2)include a trifluoromethyl group, a perfluoroethyl group, aperfluoropropyl group, a perfluoroisopropyl group, a perfluorobutylgroup, a perfluorosec-butyl group, a perfluorotert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Preferably, Q^(b1) and Q^(b2) are each independently a fluorine atom ora trifluoromethyl group, and more preferably, both are fluorine atoms.

Examples of the divalent saturated hydrocarbon group in L^(b1) include alinear alkanediyl group, a branched alkanediyl group, and a monocyclicor polycyclic divalent alicyclic saturated hydrocarbon group, or thedivalent saturated hydrocarbon group may be a group formed by combiningtwo or more of these groups.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, a dodecane-1,12-diyl group, a tridecane-1,13-diyl group, atetradecane-1,14-diyl group, a pentadecane-1,15-diyl group, ahexadecane-1,16-diyl group and a heptadecane-1,17-diyl group;

branched alkanediyl groups such as an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group;

monocyclic divalent alicyclic saturated hydrocarbon groups which arecycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and

polycyclic divalent alicyclic saturated hydrocarbon groups such as anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, anadamantane-1,5-diyl group and an adamantane-2,6-diyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— includes, forexample, a group represented by any one of formula (b1-1) to formula(b1-3). In groups represented by formula (b1-1) to formula (b1-3) andgroups represented by formula (b1-4) to formula (b1-11) which arespecific examples thereof, * and ** represent a bonding site, and *represents a bond to −Y.

In formula (b1-1),

L^(b2) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b3) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b2) and L^(b3) is 22 or less.

In formula (b1-2),

L^(b4) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b)s represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b4) and L^(b5) is 22 or less.

In formula (b1-3),

L^(b6) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group,

L^(b7) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the saturated hydrocarbon group maybe replaced by —O— or —CO—, and

the total number of carbon atoms of L^(b6) and L^(b7) is 23 or less.

In groups represented by formula (b1-1) to formula (b1-3), when —CH₂—included in the saturated hydrocarbon group is replaced by —O— or —CO—,the number of carbon atoms before replacement is taken as the number ofcarbon atoms of the saturated hydrocarbon group.

Examples of the divalent saturated hydrocarbon group include those whichare the same as the divalent saturated hydrocarbon group of L^(b1).

L^(b2) is preferably a single bond.

L^(b3) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b4) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms, and a hydrogen atom included in the divalent saturatedhydrocarbon group may be substituted with a fluorine atom.

L^(b5) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b6) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 4 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom.

L^(b7) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L^(b1) is replaced by —O— or —CO— is preferably agroup represented by formula (b1-1) or formula (b1-3).

Examples of the group represented by formula (b1-1) include groupsrepresented by formula (b1-4) to formula (b1-8).

In formula (b1-4),

L^(b8) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 22 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom or ahydroxy group.

In formula (b1-5),

L^(b9) represents a divalent saturated hydrocarbon group having 1 to 20carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—.

L^(b10) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b9) and L^(b10) is 20 or less.

In formula (b1-6),

L^(b11) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b12) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b11) and L^(b12) is 21 or less.

In formula (b1-7),

L^(b13) represents a divalent saturated hydrocarbon group having 1 to 19carbon atoms,

L^(b14) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and —CH₂— included in the divalentsaturated hydrocarbon group may be replaced by —O— or —CO—,

L^(b15) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b13) to L^(b15) is 19 or less.

In formula (b1-8),

L^(b16) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms, and —CH₂— included in the divalent saturated hydrocarbongroup may be replaced by —O— or —CO—,

L^(b17) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms,

L^(b18) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and a hydrogen atom included in thedivalent saturated hydrocarbon group may be substituted with a fluorineatom or a hydroxy group, and

the total number of carbon atoms of L^(b16) to L^(b18) is 19 or less.

L^(b8) is preferably a divalent saturated hydrocarbon group having 1 to4 carbon atoms.

L^(b9) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b10) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 19 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b11) is preferably a divalent saturated hydrocarbon group having 1 to8 carbon atoms.

L^(b12) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 8 carbon atoms.

L^(b13) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b14) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 6 carbon atoms.

L^(b15) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 18 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 8 carbon atoms.

L^(b16) is preferably a divalent saturated hydrocarbon group having 1 to12 carbon atoms.

L^(b17) is preferably a divalent saturated hydrocarbon group having 1 to6 carbon atoms.

L^(b18) is preferably a single bond or a divalent saturated hydrocarbongroup having 1 to 17 carbon atoms, and more preferably a single bond ora divalent saturated hydrocarbon group having 1 to 4 carbon atoms.

Examples of the group represented by formula (b1-3) include groupsrepresented by formula (b1-9) to formula (b1-11).

In formula (b1-9),

L^(b19) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b20) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 23 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b19) and L^(b20) is 23 or less.

In formula (b1-10),

L^(b21) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b22) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms,

L^(b23) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 21 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b21), L^(b22) and L^(b23) is 21or less.

In formula (b1-11),

L^(b24) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom,

L^(b25) represents a divalent saturated hydrocarbon group having 1 to 21carbon atoms,

L^(b26) represents a single bond or a divalent saturated hydrocarbongroup having 1 to 20 carbon atoms, a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a fluorine atom, ahydroxy group or an alkylcarbonyloxy group, —CH₂— included in thealkylcarbonyloxy group may be replaced by —O— or —CO—, and a hydrogenatom included in the alkylcarbonyloxy group may be substituted with ahydroxy group, and

the total number of carbon atoms of L^(b24), L^(b25) and L^(b26) is 21or less.

In groups represented by formula (b1-9) to formula (b1-11), when ahydrogen atom included in the saturated hydrocarbon group is substitutedwith an alkylcarbonyloxy group, the number of carbon atoms beforesubstitution is taken as the number of carbon atoms of the saturatedhydrocarbon group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy group,an adamantylcarbonyloxy group and the like.

Examples of the group represented by formula (b1-4) include thefollowings:

Examples of the group represented by formula (b1-5) include thefollowings:

Examples of the group represented by formula (b1-6) include thefollowings:

Examples of the group represented by formula (b1-7) include thefollowings:

Examples of the group represented by formula (b1-8) include thefollowings:

Examples of the group represented by formula (b1-2) include thefollowings:

Examples of the group represented by formula (b1-9) include thefollowings:

Examples of the group represented by formula (b1-10) include thefollowings:

Examples of the group represented by formula (b1-11) include thefollowings:

Examples of the alicyclic hydrocarbon group represented by Y includegroups represented by formula (Y1) to formula (Y11) and formula (Y36) toformula (Y38).

When —CH₂— included in the alicyclic hydrocarbon group represented by Yis replaced by —O—, —S(O)₂— or —CO—, the number may be 1, or 2 or more.Examples of such group include groups represented by formula (Y12) toformula (Y35) and formula (Y39) to formula (Y41).

The alicyclic hydrocarbon group represented by Y is preferably a grouprepresented by any one of formula (Y1) to formula (Y20), formula (Y26),formula (Y27), formula (Y30), formula (Y31) and formula (Y39) or formula(Y40), more preferably a group represented by formula (Y11), formula(Y15), formula (Y16), formula (Y20), formula (Y26), formula (Y27),formula (Y30), formula (Y31), formula (Y39) or formula (Y40), and stillmore preferably a group represented by formula (Y11), formula (Y15),formula (Y20), formula (Y26), formula (Y27), formula (Y30), formula(Y31), formula (Y39) or formula (Y40).

When the alicyclic hydrocarbon group represented by Y is a spiro ringsuch as formula (Y28) to formula (Y35) and formula (Y39) or formula(Y40), the alkanediyl group between two oxygen atoms preferably has oneor more fluorine atoms. Of alkanediyl groups included in a ketalstructure, it is preferable that a methylene group adjacent to theoxygen atom is not substituted with a fluorine atom.

Examples of the substituent of the methyl group represented by Y includea halogen atom, a hydroxy group, an alicyclic hydrocarbon group having 3to 16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, a glycidyloxy group, a —(CH₂)_(ja)—CO—O—R^(b1) group or a—(CH₂)_(ja)—O—CO—R^(b1) group (wherein R^(b1) represents an alkyl grouphaving 1 to 16 carbon atoms, an alicyclic hydrocarbon group having 3 to16 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms or groups obtained by combining these groups, —CH₂— included inthe alkyl group and the alicyclic hydrocarbon group may be replaced by—O—, —SO₂— or —CO—, a hydrogen atom included in the alkyl group, thealicyclic hydrocarbon group and the aromatic hydrocarbon group may besubstituted with a hydroxy group or a fluorine atom, and ja representsan integer of 0 to 4) and the like.

Examples of the substituent of the alicyclic hydrocarbon grouprepresented by Y include a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 12 carbon atoms which may be substituted with a hydroxygroup, an alicyclic hydrocarbon group having 3 to 16 carbon atoms, analkoxy group having 1 to 12 carbon atoms, an aromatic hydrocarbon grouphaving 6 to 18 carbon atoms, an aralkyl group having 7 to 21 carbonatoms, an alkylcarbonyl group having 2 to 4 carbon atoms, a glycidyloxygroup, a —(CH₂)_(ja)—CO—O—R^(b1) group or —(CH₂)_(ja)—O—CO—R^(b1) group(wherein R^(b1) represents an alkyl group having 1 to 16 carbon atoms,an alicyclic hydrocarbon group having 3 to 16 carbon atoms, an aromatichydrocarbon group having 6 to 18 carbon atoms or groups obtained bycombining these groups, —CH₂— included in the alkyl group and thealicyclic hydrocarbon group may be replaced by —O—, —SO₂— or —CO—, ahydrogen atom included in the alkyl group, the alicyclic hydrocarbongroup and the aromatic hydrocarbon group may be substituted with ahydroxy group or a fluorine atom, and ja represents an integer of 0 to4) and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a methylcyclohexyl group, a dimethylcyclohexylgroup, a cycloheptyl group, a cyclooctyl group, a norbornyl group, anadamantyl group and the like.

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group. The aromatic hydrocarbon group may have a chainhydrocarbon group or an alicyclic hydrocarbon group and examples of thearomatic hydrocarbon group having a chain hydrocarbon group include atolyl group, a xylyl group, a cumenyl group, a mesityl group, ap-ethylphenyl group, a p-tert-butylphenyl group, a 2,6-diethylphenylgroup and a 2-methyl-6-ethylphenyl group, and examples of the aromatichydrocarbon group having an alicyclic hydrocarbon group include ap-cyclohexylphenyl group, a p-adamantylphenyl group and the like.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group, an octyl group, a nonyl group, a decyl group, anundecyl group, a dodecyl group and the like.

Examples of the alkyl group substituted with a hydroxy group includehydroxyalkyl groups such as a hydroxymethyl group and a hydroxyethylgroup.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the aralkyl group include a benzyl group, a phenethyl group,a phenylpropyl group, a naphthylmethyl group and a naphthylethyl group.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of Y include the followings.

Y is preferably an alicyclic hydrocarbon group having 3 to 18 carbonatoms which may have a substituent, more preferably an adamantyl groupwhich may have a substituent, and —CH₂— constituting the alicyclichydrocarbon group or the adamantyl group may be replaced by —CO—,—S(O)₂— or —CO—. Y is still more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or groups represented bythe following formulas.

The anion in the salt represented by formula (B1) is preferably anionsrepresented by formula (B1-A-1) to formula (B1-A-55) [hereinaftersometimes referred to as “anion (B1-A-1)” according to the number offormula], and more preferably an anion represented by any one of formula(B1-A-1) to formula (B1-A-4), formula (B1-A-9), formula (B1-A-10),formula (B1-A-24) to formula (B1-A-33), formula (B1-A-36) to formula(B1-A-40) and formula (B1-A-47) to formula (B1-A-55).

R^(i2) to R^(i7) each independently represent, for example, an alkylgroup having 1 to 4 carbon atoms, and preferably a methyl group or anethyl group. R^(i8) is, for example, chain hydrocarbon group having 1 to12 carbon atoms, preferably an alkyl group having 1 to 4 carbon atoms,an alicyclic hydrocarbon group having 5 to 12 carbon atoms or groupsformed by combining these groups, and more preferably a methyl group, anethyl group, a cyclohexyl group or an adamantyl group. L^(A41) is asingle bond or an alkanediyl group having 1 to 4 carbon atoms. Q^(b1)and Q^(b2) are the same as defined above.

Specific examples of the anion in the salt represented by formula (B1)include anions mentioned in JP 2010-204646 A.

The anion in the salt represented by formula (B1) preferably includesanions represented by formula (B1a-1) to formula (B1a-34).

Of these, an anion represented by any one of formula (B1a-1) to formula(B1a-3) and formula (B1a-7) to formula (B1a-16), formula (B1a-18),formula (B1a-19) and formula (B1a-22) to formula (B1a-34) is preferable.

Examples of the organic cation of Z1⁺ include an organic onium cation,an organic sulfonium cation, an organic iodonium cation, an organicammonium cation, a benzothiazolium cation and an organic phosphoniumcation. Of these, an organic sulfonium cation and an organic iodoniumcation are preferable, and an aryl sulfonium cation is more preferable.

Examples of Z1⁺ in formula (B1) include those which are the same as thatin the salt (I).

The acid generator (B) is a combination of the anion mentioned above andthe organic cation mentioned above, and these can be optionallycombined. The acid generator (B) preferably includes a combination of ananion represented by any one of formula (B1a-1) to formula (B1a-3),formula (B1a-7) to formula (B1a-16), formula (B1a-18), formula (B1a-19)and formula (B1a-22) to formula (B1a-34) with a cation (b2-1) or acation (b2-3).

The acid generator (B) preferably includes those represented by formula(B1-1) to formula (B1-48), and of these acid generators, thosecontaining an arylsulfonium cation are preferable and those representedby formula (B1-1) to formula (B1-3), formula (B1-5) to formula (B1-7),formula (B1-11) to formula (B1-14), formula (B1-20) to formula (B1-26),formula (B1-29) and formula (B1-31) to formula (B1-48) are particularlypreferable.

When the salt (I) and the acid generator (B) are included as the acidgenerator, a ratio of the content of the salt (I) and that of the acidgenerator (B) (mass ratio; salt (I):acid generator (B)) is usually 1:99to 99:1, preferably 2:98 to 98:2, more preferably 5:95 to 95:5, stillmore preferably 10:90 to 90:10, and particularly preferably 15:85 to85:15.

<Resist Composition>

The resist composition of the present invention includes an acidgenerator including a salt (I) and a resin having an acid-labile group(hereinafter sometimes referred to as “resin (A)”). The “acid-labilegroup” means a group having a leaving group which is eliminated bycontact with an acid, thus converting a constitutional unit into aconstitutional unit having a hydrophilic group (e.g. a hydroxy group ora carboxy group).

The resist composition of the present invention preferably includes aquencher such as a salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (hereinafter sometimesreferred to as “quencher (C)”), and preferably includes a solvent(hereinafter sometimes referred to as “solvent (E)”).

<Resin (A)>

The resin (A) includes a structural unit having an acid-labile group(hereinafter sometimes referred to as “structural unit (a1)”). It ispreferable that the resin (A) further includes a structural unit otherthan the structural unit (a1). Examples of the structural unit otherthan the structural unit (a1) include a structural unit having noacid-labile group (hereinafter sometimes referred to as “structural unit(s)”), a structural unit other than the structural unit (a1) and thestructural unit (s) (e.g. a structural unit having a halogen atommentioned later (hereinafter sometimes referred to as “structural unit(a4)”), a structural unit having a non-leaving hydrocarbon groupmentioned later (hereinafter sometimes referred to as “structural unit(a5)) and other structural units derived from monomers known in the art.

<Structural Unit (a1)>

The structural unit (a1) is derived from a monomer having an acid-labilegroup (hereinafter sometimes referred to as “monomer (a1)”).

The acid-labile group contained in the resin (A) is preferably a grouprepresented by formula (1) (hereinafter also referred to as group (1))and/or a group represented by formula (2) (hereinafter also referred toas group (2)):

wherein, in formula (1), R^(a1), R^(a2) and R^(a3) each independentlyrepresent an alkyl group having 1 to 8 carbon atoms, an alicyclichydrocarbon group having 3 to 20 carbon atoms or groups obtained bycombining these groups, or R^(a1) and R^(a2) are bonded to each other toform an alicyclic hydrocarbon group having 3 to 20 carbon atoms togetherwith carbon atoms to which R^(a1) and R^(a2) are bonded,

ma and na each independently represent 0 or 1, and at least one of maand na represents 1, and

* represents a bond:

wherein, in formula (2), R^(a1′) and R^(a2′) each independentlyrepresent a hydrogen atom or a hydrocarbon group having 1 to 12 carbonatoms, R^(a3′) represents a hydrocarbon group having 1 to 20 carbonatoms, or R^(a2′) and R^(a3′) are bonded to each other to form aheterocyclic ring having 3 to 20 carbon atoms together with carbon atomsand X to which R^(a2′) and R^(a3′) are bonded, and —CH₂— included in thehydrocarbon group and the heterocyclic ring may be replaced by —O— or—S—,

X represents an oxygen atom or a sulfur atom,

na′ represents 0 or 1, and

* represents a bond.

Examples of the alkyl group in R^(a1), R^(a2) and R^(a3) include amethyl group, an ethyl group, a propyl group, a butyl group, a pentylgroup, a hexyl group, a heptyl group, an octyl group and the like.

The alicyclic hydrocarbon group in R^(a1), R^(a2) and R^(a3) may beeither monocyclic or polycyclic. Examples of the monocyclic alicyclichydrocarbon group include cycloalkyl groups such as a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group. Examplesof the polycyclic alicyclic hydrocarbon group include adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bond). The number of carbon atoms ofthe alicyclic hydrocarbon group of R^(a1), R^(a2) and R^(a3) ispreferably 3 to 16.

The group obtained by combining an alkyl group with an alicyclichydrocarbon group includes, a for example, a methylcyclohexyl group, adimethylcyclohexyl group, a methylnorbornyl group, a cyclohexylmethylgroup, an adamantylmethyl group, an adamantyldimethyl group, anorbornylethyl group and the like.

Preferably, ma is 0 and na is 1.

When R^(a1) and R^(a2) are bonded to each other to form an alicyclichydrocarbon group, examples of −C(R^(a1))(R^(a2))(R^(a3)) include thefollowing groups. The alicyclic hydrocarbon group preferably has 3 to 12carbon atoms. * represents a bond to —O—.

Examples of the hydrocarbon group in R^(a1′), R^(a2′) and R^(a3′)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group and groups obtained by combining these groups.

Examples of the alkyl group and the alicyclic hydrocarbon group includethose which are the same as mentioned in R^(a1), R^(a2) and R^(a3).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the group combined include a group obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g., acycloalkylalkyl group), an aralkyl group (a benzyl group, etc.), anaromatic hydrocarbon group having an alkyl group (a p-methylphenylgroup, a p-tert-butylphenyl group, a tolyl group, a xylyl group, acumenyl group, a mesityl group, a 2,6-diethylphenyl group, a2-methyl-6-ethylphenyl group, etc.), an aromatic hydrocarbon grouphaving an alicyclic hydrocarbon group (a p-cyclohexylphenyl group, ap-adamantylphenyl group, etc.), an aryl-cycloalkyl group (aphenylcyclohexyl group, etc.), and the like.

Examples of the heterocyclic ring formed by bonding R^(a2′) and R^(a3′)to each other together with carbon atoms and X to which R^(a2′) andR^(a3′) are bonded include the following groups. * represents a bond.

Of R^(a1′) and R^(a2′), at least one is preferably a hydrogen atom.

na′ is preferably 0.

Examples of the group (1) include the following groups.

A group wherein, in formula (1), R^(a1), R^(a2) and R^(a3) are alkylgroups, ma=0 and na=1. The group is preferably a tert-butoxycarbonylgroup.

A group wherein, in formula (1), R^(a1) and R^(a2) are bonded to eachother to form an adamantyl group together with carbon atoms to whichR^(a1) and R^(a2) are bonded, R^(a3) is an alkyl group, ma=0 and na=1.

A group wherein, in formula (1), R^(a1) and R^(a2) are eachindependently an alkyl group, R^(a3) is an adamantyl group, ma=0 andna=1.

Specific examples of the group (1) include the following groups. *represents a bond.

Specific examples of the group (2) include the following groups. *represents a bond.

The monomer (a1) is preferably a monomer having an acid-labile group andan ethylenic unsaturated bond, and more preferably a (meth)acrylicmonomer having an acid-labile group.

Of the (meth)acrylic monomers having an acid-labile group, those havingan alicyclic hydrocarbon group having 5 to 20 carbon atoms arepreferably exemplified. When a resin (A) including a structural unitderived from a monomer (a1) having a bulky structure such as analicyclic hydrocarbon group is used in a resist composition, it ispossible to improve the resolution of a resist pattern.

The structural unit derived from a (meth)acrylic monomer having a group(1) includes a structural unit represented by formula (a1-0)(hereinafter sometimes referred to as structural unit (a1-0)), astructural unit represented by formula (a1-1) (hereinafter sometimesreferred to as structural unit (a1-1)) or a structural unit representedby formula (a1-2) (hereinafter sometimes referred to as structural unit(a1-2)). Preferably, the structural unit is at least one structural unitselected from the group consisting of a structural unit (a1-1) and astructural unit (a1-2). These structural units may be used alone, or twoor more structural units may be used in combination.

In formula (a1-0), formula (a1-1) and formula (a1-2),

L^(a01), L^(a1) and L^(a2) each independently represent —O— or*—O—(CH₂)_(k1)—CO—O—, k1 represents an integer of 1 to 7, and *represents a bond to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,

R^(a02), R^(a03) and R^(a04) each independently represent an alkyl grouphaving 1 to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to18 carbon atoms or groups obtained by combining these groups,

R^(a6) and R^(a7) each independently represent an alkyl group having 1to 8 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms or groups obtained by combining these groups,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

R^(a01), R^(a4) and R^(a5) are preferably a methyl group.

L^(a01), L^(a1) and L^(a2) are preferably an oxygen atom or*—O—(CH₂)_(k01)—CO—O— (in which k01 is preferably an integer of 1 to 4,and more preferably 1), and more preferably an oxygen atom.

Examples of the alkyl group, the alicyclic hydrocarbon group and groupsobtained by combining these groups in R^(a02), R^(a03), R^(a04), R^(a6)and R^(a7) include the same groups as mentioned for R^(a1), R^(a2) andR^(a3) of formula (1).

The alkyl group in R^(a02), R^(a03) and R^(a04) is preferably an alkylgroup having 1 to 6 carbon atoms, more preferably a methyl group or anethyl group, and still more preferably a methyl group.

The alkyl group in R^(a6) and R^(a7) is preferably an alkyl group having1 to 6 carbon atoms, more preferably a methyl group, an ethyl group oran isopropyl group, and still more preferably an ethyl group or anisopropyl group.

The number of carbon atoms of the alicyclic hydrocarbon group ofR^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) is preferably 5 to 12, andmore preferably 5 to 10.

The total number of carbon atoms of the group obtained by combining thealkyl group with the alicyclic hydrocarbon group is preferably 18 orless.

R^(a02) and R^(a03) are preferably an alkyl group having 1 to 6 carbonatoms, and more preferably a methyl group or an ethyl group.

R^(a04) is preferably an alkyl group having 1 to 6 carbon atoms or analicyclic hydrocarbon group having 5 to 12 carbon atoms, and morepreferably a methyl group, an ethyl group, a cyclohexyl group or anadamantyl group.

Preferably, R^(a6) and R^(a7) are each independently an alkyl grouphaving 1 to 6 carbon atoms, more preferably a methyl group, an ethylgroup or an isopropyl group, and still more preferably an ethyl group oran isopropyl group.

m1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

n1′ is preferably 0 or 1.

The structural unit (a1-0) includes, for example, a structural unitrepresented by any one of formula (a1-0-1) to formula (a1-0-12) and astructural unit in which a methyl group corresponding to R^(a01) in thestructural unit (a1-0) is substituted with a hydrogen atom and ispreferably a structural unit represented by any one of formula (a1-0-1)to formula (a1-0-10).

The structural unit (a1-1) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. Of thesestructural units, a structural unit represented by any one of formula(a1-1-1) to formula (a1-1-4) and a structural unit in which a methylgroup corresponding to R^(a4) in the structural unit (a1-1) issubstituted with a hydrogen atom are preferable, and a structural unitrepresented by any one of formula (a1-1-1) to formula (a1-1-4) is morepreferable.

Examples of the structural unit (a1-2) include a structural unitrepresented by any one of formula (a1-2-1) to formula (a1-2-6) and astructural unit in which a methyl group corresponding to R^(a5) in thestructural unit (a1-2) is substituted with a hydrogen atom, andstructural units represented by formula (a1-2-2), formula (a1-2-5) andformula (a1-2-6) are preferable.

When the resin (A) includes a structural unit (a1-0) and/or a structuralunit (a1-1) and/or a structural unit (a1-2), the total content thereofis usually 10 to 95 mol %, preferably 15 to 90 mol %, more preferably 20to 85 mol %, still more preferably 25 to 70 mol %, and yet morepreferably 30 to 70 mol %, based on all structural units of the resin(A).

In the structural unit (a1), examples of the structural unit having agroup (2) include a structural unit represented by formula (a1-4)(hereinafter sometimes referred to as “structural unit (a1-4)”):

wherein, in formula (a1-4),

R^(a32) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a33) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxygroup having 2 to 4 carbon atoms, an acryloyloxy group or amethacryloyloxy group.

la represents an integer of 0 to 4, and when la is 2 or more, aplurality of R^(a33) may be the same or different from each other, and

R^(a34) and R^(a35) each independently represent a hydrogen atom or ahydrocarbon group having 1 to 12 carbon atoms, R^(a36) represents ahydrocarbon group having 1 to 20 carbon atoms, or R^(a35) and R^(a36)are bonded to each other to form a divalent hydrocarbon group having 2to 20 carbon atoms together with —C—O— to which R^(a35) and R^(a36) arebonded, and —CH₂— included in the hydrocarbon group and the divalenthydrocarbon group may be replaced by —O— or —S—.

Examples of the alkyl group in R^(a32) and R^(a33) include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a pentyl group and a hexyl group. The alkyl group is preferablyan alkyl group having 1 to 4 carbon atoms, more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom in R^(a32) and R^(a33) include a fluorineatom, a chlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom include a trifluoromethyl group, a difluoromethyl group, amethyl group, a perfluoroethyl group, a 2,2,2-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 2,2,3,3,3-pentafluoropropyl group, a propyl group, a perfluorobutylgroup, a 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, a 2,2,3,3,4,4,5,5,5-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group and the like.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group and a hexyloxy group.Of these groups, an alkoxy group having 1 to 4 carbon atoms ispreferable, a methoxy group or an ethoxy group are more preferable, anda methoxy group is still more preferable.

Examples of the alkylcarbonyl group include an acetyl group, a propionylgroup and a butyryl group.

Examples of the alkylcarbonyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group and the like.

Examples of the hydrocarbon group in R^(a34), R^(a35) and R^(a36)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group, and groups formed by combining these groups.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group and the like.

The alicyclic hydrocarbon group may be either monocyclic or polycyclic.Examples of the monocyclic alicyclic hydrocarbon group includecycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group. Examples of the polycyclicalicyclic hydrocarbon group include a decahydronaphthyl group, anadamantyl group, a norbornyl group and the following groups (*represents a bonding site).

Examples of the aromatic hydrocarbon group include aryl groups such as aphenyl group, a naphthyl group, an anthryl group, a biphenyl group and aphenanthryl group.

Examples of the combined group include groups obtained by combining theabove-mentioned alkyl group and alicyclic hydrocarbon group (e.g.,cycloalkylalkyl group), aralkyl groups such as a benzyl group, aromatichydrocarbon groups having an alkyl group (a p-methylphenyl group, ap-tert-butylphenyl group, a tolyl group, a xylyl group, a cumenyl group,a mesityl group, a 2,6-diethylphenyl group, a 2-methyl-6-ethylphenylgroup, etc.), aromatic hydrocarbon groups having an alicyclichydrocarbon group (a p-cyclohexylphenyl group, a p-adamantylphenylgroup, etc.), aryl-cyclohexyl groups such as a phenylcyclohexyl groupand the like. Particularly, examples of R^(a36) include an alkyl grouphaving 1 to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to18 carbon atoms, an aromatic hydrocarbon group having 6 to 18 carbonatoms, or groups formed by combining these groups.

In formula (a1-4), R^(a32) is preferably a hydrogen atom,

R^(a33) is preferably an alkoxy group having 1 to 4 carbon atoms, morepreferably a methoxy group and an ethoxy group, and still morepreferably a methoxy group,

la is preferably 0 or 1, and more preferably 0,

R^(a34) is preferably a hydrogen atom, and

R^(a35) is preferably an alkyl group having 1 to 12 carbon atoms or analicyclic hydrocarbon group, and more preferably a methyl group or anethyl group.

The hydrocarbon group of R^(a36) is preferably an alkyl group having 1to 18 carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, an aromatic hydrocarbon group having 6 to 18 carbon atoms orgroups formed by combining these groups, and more preferably an alkylgroup having 1 to 18 carbon atoms, an alicyclic aliphatic hydrocarbongroup having 3 to 18 carbon atoms or an aralkyl group having 7 to 18carbon atoms. The alkyl group and the alicyclic hydrocarbon group inR^(a36) are preferably unsubstituted. The aromatic hydrocarbon group inR^(a36) is preferably an aromatic ring having an aryloxy group having 6to 10 carbon atoms.

—OC(R^(a34))(R^(a35))—O—R^(a36) in the structural unit (a1-4) iseliminated by contacting with an acid (e.g., p-toluenesulfonic acid) toform a hydroxy group.

The structural unit (a1-4) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. The structuralunit preferably includes structural units represented by formula(a1-4-1) to formula (a1-4-12) and a structural unit in which a hydrogenatom corresponding to R^(a32) in the constitutional unit (a1-4) issubstituted with a methyl group, and more preferably structural unitsrepresented by formula (a1-4-1) to formula (a1-4-5) and formula(a1-4-10).

When the resin (A) includes the structural unit (a1-4), the content ispreferably 10 to 95 mol %, more preferably 15 to 90 mol %, still morepreferably 20 to 85 mol %, yet more preferably 20 to 70 mol %, andparticularly preferably 20 to 60 mol %, based on the total of allstructural units of the resin (A).

The structural unit derived from a (meth)acrylic monomer having a group(2) also includes a structural unit represented by formula (a1-5)(hereinafter sometimes referred to as “structural unit (a1-5)”).

In formula (a1-5),

R^(a8) represents an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, a hydrogen atom or a halogen atom,

Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴-, h3 representsan integer of 1 to 4, and * represents a bond to L⁵¹,

L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent —O— or —S—,

s1 represents an integer of 1 to 3, and

s1′ represents an integer of 0 to 3.

The halogen atom includes a fluorine atom and a chlorine atom and ispreferably a fluorine atom. Examples of the alkyl group having 1 to 6carbon atoms which may have a halogen atom include a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a fluoromethyl group and atrifluoromethyl group.

In formula (a1-5), R^(a8) is preferably a hydrogen atom, a methyl groupor a trifluoromethyl group,

L⁵¹ is preferably an oxygen atom,

one of L⁵² and L⁵³ is preferably —O— and the other one is preferably—S—,

s1 is preferably 1,

s1′ is preferably an integer of 0 to 2, and

Z^(a1) is preferably a single bond or *—CH₂—CO—O—.

The structural unit (a1-5) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-61117 A. Of thesestructural units, structural units represented by formula (a1-5-1) toformula (a1-5-4) are preferable, and structural units represented byformula (a1-5-1) or formula (a1-5-2) are more preferable.

When the resin (A) includes the structural unit (a1-5), the content ispreferably 1 to 50 mol %, more preferably 3 to 45 mol %, still morepreferably 5 to 40 mol %, and yet more preferably 5 to 30 mol %, basedon all structural units of the resin (A).

The structural unit (a1) also includes the following structural units.

When the resin (A) includes the above-mentioned structural units such as(a1-3-1) to (a1-3-7), the content is preferably 10 to 95 mol %, morepreferably 15 to 90 mol %, still more preferably 20 to 85 mol %, yetmore preferably 20 to 70 mol %, and particularly preferably 20 to 60 mol%, based on all structural units of the resin (A).

<Structural Unit (s)>

The structural unit (s) is derived from a monomer having no acid-labilegroup (hereinafter sometimes referred to as “monomer (s)”). It ispossible to use, as the monomer from which the structural unit (s) isderived, a monomer having no acid-labile group known in the resistfield.

The structural unit (s) preferably has a hydroxy group or a lactonering. When a resin including a structural unit having a hydroxy groupand having no acid-labile group (hereinafter sometimes referred to as“structural unit (a2)”) and/or a structural unit having a lactone ringand having no acid-labile group (hereinafter sometimes referred to as“structural unit (a3)”) is used in the resist composition of the presentinvention, it is possible to improve the resolution of a resist patternand the adhesion to a substrate.

<Structural Unit (a2)>

The hydroxy group possessed by the structural unit (a2) may be either analcoholic hydroxy group or a phenolic hydroxy group.

When a resist pattern is produced from the resist composition of thepresent invention, in the case of using, as an exposure source, highenergy rays such as KrF excimer laser (248 nm), electron beam or extremeultraviolet light (EUV), it is preferable to use a structural unit (a2)having a phenolic hydroxy group as the structural unit (a2). When usingArF excimer laser (193 nm) or the like, a structural unit (a2) having analcoholic hydroxy group is preferably used as the structural unit (a2),and it is more preferably use a structural unit (a2-1) mentioned later.The structural unit (a2) may be included alone, or two or morestructural units may be included.

In the structural unit (a2), examples of the structural unit having aphenolic hydroxy group include a structural unit represented by formula(a2-A) (hereinafter sometimes referred to as “structural unit (a2-A)”)

wherein, in formula (a2-A),

R^(a50) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom,

R^(a51) represents a halogen atom, a hydroxy group, an alkyl grouphaving 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms,an alkylcarbonyl group having 2 to 4 carbon atoms, an alkylcarbonyloxygroup having 2 to 4 carbon atoms, an acryloyloxy group or amethacryloyloxy group,

A^(a50) represents a single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—,and * represents a bond to carbon atoms to which —R^(a50) is bonded,

A^(a52) represents an alkanediyl group having 1 to 6 carbon atoms,

X^(a51) and X^(a52) each independently represent —O—, —CO—O— or —O—CO—,

nb represents 0 or 1, and

mb represents an integer of 0 to 4, and when mb is an integer of 2 ormore, a plurality of R^(a51) may be the same or different from eachother.

Examples of the halogen atom in R^(a50) include a fluorine atom, achlorine atom and a bromine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom in R^(a50) include a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl groupand a perfluorohexyl group.

R^(a50) is preferably a hydrogen atom or an alkyl group having 1 to 4carbon atoms, more preferably a hydrogen atom, a methyl group or anethyl group, and still more preferably a hydrogen atom or a methylgroup.

Examples of the alkyl group in R^(a51) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group.

Examples of the alkoxy group in R^(a51) include a methoxy group, anethoxy group, a propoxy group, an isopropoxy group, a butoxy group, asec-butoxy group and a tert-butoxy group. An alkoxy group having 1 to 4carbon atoms is preferable, a methoxy group or an ethoxy group is morepreferable, and a methoxy group is still more preferable.

Examples of the alkylcarbonyl group in R^(a51) include an acetyl group,a propionyl group and a butyryl group.

Examples of the alkylcarbonyloxy group in R^(a51) include an acetyloxygroup, a propionyloxy group and a butyryloxy group.

R^(a51) is preferably a methyl group.

Examples of *—X^(a51)-(A^(a52)-X^(a52))_(nb)— include *—O—, *—CO—O—,*—O—CO—, *—CO—O-A^(a52)-CO—O—, *—O—CO-A^(a2)-O—, *—O-A^(a52)-CO—O—,*—CO—O-A^(a52)-O—CO— and *—O—CO-A^(a52)-O—CO—. Of these, *—CO—O—,*—CO—O-A^(a52)-CO—O— or *—O-A^(a52)-CO—O— is preferable.

Examples of the alkanediyl group include a methylene group, an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a52) is preferably a methylene group or an ethylene group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-CO—O—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—CO—O—, and stillmore preferably a single bond or *—CO—O—.

mb is preferably 0, 1 or 2, more preferably 0 or 1, and particularlypreferably 0.

The hydroxy group is preferably bonded to the ortho-position or thepara-position of a benzene ring, and more preferably the para-position.

Examples of the structural unit (a2-A) include structural units derivedfrom the monomers mentioned in JP 2010-204634 A and JP 2012-12577 A.

Examples of the structural unit (a2-A) include structural unitsrepresented by formula (a2-2-1) to formula (a2-2-6) and a structuralunit in which a methyl group corresponding to R^(a50) in the structuralunit (a2-A) is substituted with a hydrogen atom in structural unitsrepresented by formula (a2-2-1) to formula (a2-2-6). The structural unit(a2-A) is preferably a structural unit in which a methyl groupcorresponding to R^(a50) in the structural unit (a2-A) is substitutedwith a hydrogen atom in the structural unit represented by formula(a2-2-1), the structural unit represented formula (a2-2-3), thestructural unit represented by formula (a2-2-6) and the structural unitrepresented by formula (a2-2-1), the structural unit represented byformula (a2-2-3) or the structural unit represented by formula (a2-2-6).

When the structural unit (a2-A) is included in the resin (A), thecontent of the structural unit (a2-A) is preferably 5 to 80 mol %, morepreferably 10 to 70 mol %, still more preferably 15 to 65 mol %, and yetmore preferably 20 to 65 mol %, based on all structural units.

The structural unit (a2-A) can be included in a resin (A) bypolymerizing, for example, with a structural unit (a1-4) and treatingwith an acid such as p-toluenesulfonic acid. The structural unit (a2-A)can also be included in the resin (A) by polymerizing withacetoxystyrene and treating with an alkali such as tetramethylammoniumhydroxide.

Examples of the structural unit having an alcoholic hydroxy group in thestructural unit (a2) include a structural unit represented by formula(a2-1) (hereinafter sometimes referred to as “structural unit (a2-1)”).

In formula (a2-1),

L^(a3) represents —O— or *—O—(CH₂)_(k2)—CO—O—,

k2 represents an integer of 1 to 7, and * represents a bond to —CO—,

R^(a14) represents a hydrogen atom or a methyl group,

R^(a15) and R^(a16) each independently represent a hydrogen atom, amethyl group or a hydroxy group, and

o1 represents an integer of 0 to 10.

In formula (a2-1), L^(a3) is preferably —O— or —O—(CH₂)_(f1)—CO—O— (f1represents an integer of 1 to 4), and more preferably —O—,

R^(a14) is preferably a methyl group,

R^(a15) is preferably a hydrogen atom,

R^(a16) is preferably a hydrogen atom or a hydroxy group, and

o1 is preferably an integer of 0 to 3, and more preferably 0 or 1.

The structural unit (a2-1) includes, for example, structural unitsderived from the monomers mentioned in JP 2010-204646 A. A structuralunit represented by any one of formula (a2-1-1) to formula (a2-1-6) ispreferable, a structural unit represented by any one of formula (a2-1-1)to formula (a2-1-4) is more preferable, and a structural unitrepresented by formula (a2-1-1) or formula (a2-1-3) is still morepreferable.

When the resin (A) includes the structural unit (a2-1), the content isusually 1 to 45 mol %, preferably 1 to 40 mol %, more preferably 1 to 35mol %, still more preferably 1 to 20 mol %, and yet more preferably 1 to10 mol %, based on all structural units of the resin (A).

<Structural Unit (a3)>

The lactone ring possessed by the structural unit (a3) may be amonocyclic ring such as a β-propiolactone ring, a γ-butyrolactone ringor a δ-valerolactone ring, or a condensed ring of a monocyclic lactonering and the other ring. Preferably, a γ-butyrolactone ring, anadamantanelactone ring or a bridged ring including a γ-butyrolactonering structure (e.g. a structural unit represented by the followingformula (a3-2)) is exemplified.

The structural unit (a3) is preferably a structural unit represented byformula (a3-1), formula (a3-2), formula (a3-3) or formula (a3-4). Thesestructural units may be included alone, or two or more structural unitsmay be included:

wherein, in formula (a3-1), formula (a3-2), formula (a3-3) and formula(a3-4),

L^(a4), L^(a5) and L^(a6) each independently represent —O— or a grouprepresented by *—O—(CH₂)_(k3)—CO—O— (k3 represents an integer of 1 to7),

L^(a7) represents —O—, *—O-L^(a8)-O—, *—O-L^(a8)-CO—O—,*—O-L^(a8)-CO—O-L^(a9)-CO—O— or *—O-L^(a8)-O—CO-L^(a9)-O—,

L^(a8) and L^(a9) each independently represent an alkanediyl grouphaving 1 to 6 carbon atoms,

* represents a bonding site to a carbonyl group,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a24) represents an alkyl group having 1 to 6 carbon atoms which mayhave a halogen atom, a hydrogen atom or a halogen atom,

X^(a3) represents —CH₂— or an oxygen atom,

R^(a21) represents an aliphatic hydrocarbon group having 1 to 4 carbonatoms,

R^(a22), R^(a23) and R^(a25) each independently represent a carboxygroup, a cyano group or an aliphatic hydrocarbon group having 1 to 4carbon atoms,

p1 represents an integer of 0 to 5,

q1 represents an integer of 0 to 3,

r1 represents an integer of 0 to 3,

w1 represents an integer of 0 to 8, and

when p1, q1, r1 and/or w1 is/are 2 or more, a plurality of R^(a21),R^(a22), R^(a23) and/or R^(a25) may be the same or different from eachother.

Examples of the aliphatic hydrocarbon group in R^(a21), R^(a22), R^(a23)and R^(a25) include alkyl groups such as a methyl group, an ethyl group,a propyl group, an isopropyl group, a butyl group, a sec-butyl group anda tert-butyl group.

Examples of the halogen atom in R^(a24) include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group in R^(a24) include a methyl group, an ethylgroup, a propyl group, an isopropyl group, a butyl group, a sec-butylgroup, a tert-butyl group, a pentyl group and a hexyl group, and thealkyl group is preferably an alkyl group having 1 to 4 carbon atoms, andmore preferably a methyl group or an ethyl group.

Examples of the alkyl group having a halogen atom in R^(a24) include atrifluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluoroisopropyl group, a perfluorobutyl group, a perfluorosec-butylgroup, a perfluorotert-butyl group, a perfluoropentyl group, aperfluorohexyl group, a trichloromethyl group, a tribromomethyl group, atriiodomethyl group and the like.

Examples of the alkanediyl group in L^(a8) and L^(a9) include amethylene group, an ethylene group, a propane-1,3-diyl group, apropane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group.

In formula (a3-1) to formula (a3-3), preferably, L^(a4) to L^(a6) areeach independently —O— or a group in which k3 is an integer of 1 to 4 in*—O—(CH₂)_(k3)—CO—O—, more preferably —O— and *—O—CH₂—CO—O—, and stillmore preferably an oxygen atom,

R^(a18) to R^(a21) are preferably a methyl group,

preferably, R^(a22) and R^(a23) are each independently a carboxy group,a cyano group or a methyl group, and

preferably, p1, q1 and r1 are each independently an integer of 0 to 2,and more preferably 0 or 1.

In formula (a3-4), R^(a24) is preferably a hydrogen atom or an alkylgroup having 1 to 4 carbon atoms, more preferably a hydrogen atom, amethyl group or an ethyl group, and still more preferably a hydrogenatom or a methyl group,

R^(a25) is preferably a carboxy group, a cyano group or a methyl group,

L^(a7) is preferably —O— or *—O-L^(a8)-CO—O—, and more preferably —O—,—O—CH₂—CO—O— or —O—C₂H₄—CO—O—, and

w1 is preferably an integer of 0 to 2, and more preferably 0 or 1.

Particularly, formula (a3-4) is preferably formula (a3-4)′:

wherein R^(a24) and L^(a7) are the same as defined above.

Examples of the structural unit (a3) include structural units derivedfrom the monomers mentioned in JP 2010-204646 A, the monomers mentionedin JP 2000-122294 A and the monomers mentioned in JP 2012-41274 A. Thestructural unit (a3) is preferably a structural unit represented by anyone of formula (a3-1-1), formula (a3-1-2), formula (a3-2-1), formula(a3-2-2), formula (a3-3-1), formula (a3-3-2) and formula (a3-4-1) toformula (a3-4-12), and structural units in which methyl groupscorresponding to R^(a18), R^(a19), R^(a20) and R^(a24) in formula (a3-1)to formula (a3-4) are substituted with hydrogen atoms in the abovestructural units.

When the resin (A) includes the structural unit (a3), the total contentis usually 5 to 70 mol %, preferably 10 to 65 mol %, and more preferably10 to 60 mol %, based on all structural units of the resin (A).

Each content of the structural unit (a3-1), the structural unit (a3-2),the structural unit (a3-3) or the structural unit (a3-4) is preferably 5to 60 mol %, more preferably 5 to 50 mol %, and still more preferably 10to 50 mol %, based on all structural units of the resin (A).

<Structural Unit (a4)>

Examples of the structural unit (a4) include the following structuralunits:

wherein, in formula (a4),

R⁴¹ represents a hydrogen atom or a methyl group, and

R⁴² represents a saturated hydrocarbon group having 1 to 24 carbon atomswhich has a fluorine atom, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO.

Examples of the saturated hydrocarbon group represented by R⁴² include achain hydrocarbon group and a monocyclic or polycyclic alicyclicsaturated hydrocarbon group, and groups formed by combining thesegroups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup. Examples of the monocyclic or polycyclic alicyclic hydrocarbongroup include cycloalkyl groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andpolycyclic alicyclic saturated hydrocarbon groups such as adecahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups (* represents a bond).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic hydrocarbon groups, and include an alkanediylgroup-alicyclic hydrocarbon group, an alicyclic saturated hydrocarbongroup-alkyl group, an alkanediyl group-alicyclic hydrocarbon group-alkylgroup and the like.

Examples of the structural unit (a4) include a structural unitrepresented by at least one selected from the group consisting offormula (a4-0), formula (a4-1), formula (a4-2), formula (a4-3) andformula (a4-4):

wherein, in formula (a4-0),

R⁵ represents a hydrogen atom or a methyl group,

L^(4a) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 4 carbon atoms,

L^(3a) represents a perfluoroalkanediyl group having 1 to 8 carbon atomsor a perfluorocycloalkanediyl group having 3 to 12 carbon atoms, and

R⁶ represents a hydrogen atom or a fluorine atom.

Examples of the divalent aliphatic saturated hydrocarbon group in L^(4a)include linear alkanediyl groups such as a methylene group, an ethylenegroup, a propane-1,3-diyl group and a butane-1,4-diyl group; andbranched alkanediyl groups such as an ethane-1,1-diyl group, apropane-1,2-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group and a 2-methylpropane-1,2-diyl group.

Examples of the perfluoroalkanediyl group in L^(3a) include adifluoromethylene group, a perfluoroethylene group, aperfluoropropane-1,1-diyl group, a perfluoropropane-1,3-diyl group, aperfluoropropane-1,2-diyl group, a perfluoropropane-2,2-diyl group, aperfluorobutane-1,4-diyl group, a perfluorobutane-2,2-diyl group, aperfluorobutane-1,2-diyl group, a perfluoropentane-1,5-diyl group, aperfluoropentane-2,2-diyl group, a perfluoropentane-3,3-diyl group, aperfluorohexane-1,6-diyl group, a perfluorohexane-2,2-diyl group, aperfluorohexane-3,3-diyl group, a perfluoroheptane-1,7-diyl group, aperfluoroheptane-2,2-diyl group, a perfluoroheptane-3,4-diyl group, aperfluoroheptane-4,4-diyl group, a perfluorooctane-1,8-diyl group, aperfluorooctane-2,2-diyl group, a perfluorooctane-3,3-diyl group, aperfluorooctane-4,4-diyl group and the like.

Examples of the perfluorocycloalkanediyl group in L^(3a) include aperfluorocyclohexanediyl group, a perfluorocyclopentanediyl group, aperfluorocycloheptanediyl group, a perfluoroadamantanediyl group and thelike.

L^(4a) is preferably a single bond, a methylene group or an ethylenegroup, and more preferably a single bond or a methylene group.

L^(3a) is preferably a perfluoroalkanediyl group having 1 to 6 carbonatoms, and more preferably a perfluoroalkanediyl group having 1 to 3carbon atoms.

Examples of the structural unit (a4-0) include the following structuralunits, and structural units in which a methyl group corresponding to R⁵in the structural unit (a4-0) in the following structural units issubstituted with a hydrogen atom:

wherein, in formula (a4-1),

R^(a41) represents a hydrogen atom or a methyl group,

R^(a42) represents a saturated hydrocarbon group having 1 to 20 carbonatoms which may have a substituent, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—,

A^(a41) represents an alkanediyl group having 1 to 6 carbon atoms whichmay have a substituent or a group represented by formula (a-g1), inwhich at least one of A^(a41) and R^(a42) has, as a substituent, ahalogen atom (preferably a fluorine atom):

[in which, in formula (a-g1),

s represents 0 or 1,

A^(a42) and A^(a44) each independently represent a divalent saturatedhydrocarbon group having 1 to 5 carbon atoms which may have asubstituent,

A^(a43) represents a single bond or a divalent aliphatic hydrocarbongroup having 1 to 5 carbon atoms which may have a substituent,

X^(a41) and X^(a42) each independently represent —O—, —CO—, —CO—O— or—O—CO—, in which the total number of carbon atoms of A^(a42), A^(a43),A^(a44), X^(a41) and X^(a42) is 7 or less], and

* represents a bond and * at the right side represents a bond to—O—CO—R^(a42).

Examples of the saturated hydrocarbon group in R^(a42) include a chainhydrocarbon group and a monocyclic or a polycyclic alicyclic hydrocarbongroup, and groups formed by combining these groups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a pentadecyl group, a hexadecyl group, a heptadecyl group and anoctadecyl group.

Examples of the monocyclic or polycyclic alicyclic hydrocarbon groupinclude cycloalkyl groups such as a cyclopentyl group, a cyclohexylgroup, a cycloheptyl group and a cyclooctyl group; and polycyclicalicyclic hydrocarbon groups such as a decahydronaphthyl group, anadamantyl group, a norbornyl group and the following groups (*represents a bond).

Examples of the group formed by combination include groups formed bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic saturated hydrocarbon groups, and include analkanediyl group-alicyclic saturated hydrocarbon group, an alicyclicsaturated hydrocarbon group-alkyl group, an alkanediyl group-alicyclicsaturated hydrocarbon group-alkyl group and the like.

Examples of the substituent which may be possessed by R^(a42) include atleast one selected from the group consisting of a halogen atom and agroup represented by formula (a-g3). Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is preferable:

*—X^(a43)-A^(a45)  (a-g3)

wherein, in formula (a-g3),

X^(a43) represents an oxygen atom, a carbonyl group, **—O—CO— or**—CO—O— (** represents a bond to R^(a42)),

A^(a45) represents a aliphatic hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom, and

* represents a bond.

In R^(a42)—X^(a43)-A^(a45), when R^(a42) has no halogen atom, A^(a45)represents an aliphatic hydrocarbon group having 1 to 17 carbon atomshaving at least one halogen atom.

Examples of the aliphatic hydrocarbon group in A^(a45) include alkylgroups such as a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group, an octyl group, adecyl group, a dodecyl group, a pentadecyl group, a hexadecyl group, aheptadecyl group and an octadecyl group; monocyclic alicyclichydrocarbon groups such as a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group; and polycyclic alicyclichydrocarbon groups such as a decahydronaphthyl group, an adamantylgroup, a norbornyl group and the following groups (* represents a bond):

Examples of the group formed by combination include a group obtained bycombining one or more alkyl groups or one or more alkanediyl groups withone or more alicyclic hydrocarbon groups, and include an -alkanediylgroup-alicyclic hydrocarbon group, an -alicyclic hydrocarbon group-alkylgroup, an -alkanediyl group-alicyclic hydrocarbon group-alkyl group andthe like.

R^(a42) is preferably an aliphatic hydrocarbon group which may have ahalogen atom, and more preferably an alkyl group having a halogen atomand/or an aliphatic hydrocarbon group having a group represented byformula (a-g3).

When R^(a42) is an aliphatic hydrocarbon group having a halogen atom, analiphatic hydrocarbon group having a fluorine atom is preferable, aperfluoroalkyl group or a perfluorocycloalkyl group is more preferable,a perfluoroalkyl group having 1 to 6 carbon atoms is still morepreferable, and a perfluoroalkyl group having 1 to 3 carbon atoms isparticularly preferable. Examples of the perfluoroalkyl group include aperfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group,a perfluorobutyl group, a perfluoropentyl group, a perfluorohexyl group,a perfluoroheptyl group and a perfluorooctyl group. Examples of theperfluorocycloalkyl group include a perfluorocyclohexyl group and thelike.

When R^(a42) is an aliphatic hydrocarbon group having a grouprepresented by formula (a-g3), the total number of carbon atoms ofR^(a42) is preferably 15 or less, and more preferably 12 or less,including the number of carbon atoms included in the group representedby formula (a-g3). When having the group represented by formula (a-g3)as the substituent, the number thereof is preferably 1.

When R^(a42) is an aliphatic hydrocarbon group having the grouprepresented by formula (a-g3), R^(a42) is still more preferably a grouprepresented by formula (a-g2):

*-A^(a46)-X^(a44)-A^(a47)  (a-g2)

wherein, in formula (a-g2),

A^(a46) represents an aliphatic hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom,

X^(a44) represents **—O—CO— or **—CO—O— (** represents a bond toA^(a46)),

A^(a47) represents an aliphatic hydrocarbon group having 1 to 17 carbonatoms which may have a halogen atom,

the total number of carbon atoms of A^(a46), A^(a47) and X^(a44) is 18or less, and at least one of A^(a46) and A^(a47) has at least onehalogen atom, and

* represents a bond to a carbonyl group.

The number of carbon atoms of the aliphatic hydrocarbon group of A^(a46)is preferably 1 to 6, and more preferably 1 to 3.

The number of carbon atoms of the aliphatic hydrocarbon group of A^(a47)is preferably 4 to 15, and more preferably 5 to 12, and A^(a47) is stillmore preferably a cyclohexyl group or an adamantyl group.

Preferred structure of the group represented by formula (a-g2) is thefollowing structure (* represents a bond to a carbonyl group).

Examples of the alkanediyl group in A^(a41) include linear alkanediylgroups such as a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a pentane-1,5-diyl group and ahexane-1,6-diyl group; and branched alkanediyl groups such as apropane-1,2-diyl group, a butane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a 1-methylbutane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Examples of the substituent in the alkanediyl group of A^(a41) include ahydroxy group and an alkoxy group having 1 to 6 carbon atoms.

A^(a41) is preferably an alkanediyl group having 1 to 4 carbon atoms,more preferably an alkanediyl group having 2 to 4 carbon atoms, andstill more preferably an ethylene group.

Examples of the divalent saturated hydrocarbon group represented byA^(a42), A^(a43) and A^(a44) in the group represented by formula (a-g1)include a linear or branched alkanediyl group and a monocyclic divalentalicyclic hydrocarbon group, and groups formed by combining analkanediyl group and a divalent alicyclic hydrocarbon group. Specificexamples thereof include a methylene group, an ethylene group, apropane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diylgroup, a 1-methylpropane-1,3-diyl group, a 2-methylpropane-1,3-diylgroup, a 2-methylpropane-1,2-diyl group and the like.

Examples of the substituent of the divalent saturated hydrocarbon grouprepresented by A^(a42), A^(a43) and A^(a44) include a hydroxy group andan alkoxy group having 1 to 6 carbon atoms.

s is preferably 0.

In the group represented by formula (a-g2), examples of the group inwhich X^(a42) is —O—, —CO—, —CO—O— or —O—CO— include the followinggroups. In the following exemplification, * and ** each represent abond, and ** represents a bond to —O—CO—R^(a42).

Examples of the structural unit represented by formula (a4-1) includethe following structural units, and structural units in which a methylgroup corresponding to A^(a41) in the structural unit represented byformula (a4-1) in the following structural units is substituted with ahydrogen atom.

Examples of the structural unit represented by formula (a4-1) include astructural unit represented by formula (a4-2):

wherein, in formula (a4-2),

R^(f5) represents a hydrogen atom or a methyl group,

L⁴⁴ represents an alkanediyl group having 1 to 6 carbon atoms, and —CH₂—included in the alkanediyl group may be replaced by —O— or —CO—,

R^(f6) represents a saturated hydrocarbon group having 1 to 20 carbonatoms having a fluorine atom, and

the upper limit of the total number of carbon atoms of L⁴⁴ and R^(f6) is21.

Examples of the alkanediyl group having 1 to 6 carbon atoms of L⁴⁴include the same groups as mentioned for the alkanediyl group inA^(a41).

Examples of the saturated hydrocarbon group of R^(f6) include the samegroups as mentioned for R^(a42).

The alkanediyl group having 1 to 6 carbon atoms in L⁴⁴ is preferably analkanediyl group having 2 to 4 carbon atoms, and more preferably anethylene group.

The structural unit represented by formula (a4-2) includes, for example,structural units represented by formula (a4-1-1) to formula (a4-1-11). Astructural unit in which a methyl group corresponding to R^(f5) in thestructural unit (a4-2) is substituted with a hydrogen atom is alsoexemplified as the structural unit represented by formula (a4-2):

Examples of the structural unit (a4) include a structural unitrepresented by formula (a4-3):

wherein, in formula (a4-3),

R^(f7) represents a hydrogen atom or a methyl group,

L⁵ represents an alkanediyl group having 1 to 6 carbon atoms,

A^(f13) represents a divalent saturated hydrocarbon group having 1 to 18carbon atoms which may have a fluorine atom,

X^(f12) represents *—O—CO— or *—CO—O— (* represents a bond to A^(f13)),

A^(f14) represents a saturated hydrocarbon group having 1 to 17 carbonatoms which may have a fluorine atom, and

at least one of A^(f13) and A^(f14) has a fluorine atom, and the upperlimit of the total number of carbon atoms of L⁵, A^(f13) and A^(f14) is20.

Examples of the alkanediyl group in L⁵ include those which are the sameas mentioned in the alkanediyl group of A^(a41).

The divalent saturated hydrocarbon group which may have a fluorine atomin A^(f13) is preferably a divalent aliphatic saturated hydrocarbongroup which may have a fluorine atom and a divalent alicyclic saturatedhydrocarbon group which may have a fluorine atom, and more preferably aperfluoroalkanediyl group.

Examples of the divalent aliphatic saturated hydrocarbon group which mayhave a fluorine atom include alkanediyl groups such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group and apentanediyl group; and perfluoroalkanediyl groups such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group and aperfluoropentanediyl group.

The divalent aliphatic saturated hydrocarbon group which may have afluorine atom may be either monocyclic or polycyclic. Examples of themonocyclic group include a cyclohexanediyl group and aperfluorocyclohexanediyl group. Examples of the polycyclic group includean adamantanediyl group, a norbornanediyl group, aperfluoroadamantanediyl group and the like.

Examples of the saturated hydrocarbon group and the saturatedhydrocarbon group which may have a fluorine atom for A^(f14) include thesame groups as mentioned for R^(a42). Of these groups, preferable arefluorinated alkyl groups such as a trifluoromethyl group, adifluoromethyl group, a methyl group, a perfluoroethyl group, a2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, an ethylgroup, a perfluoropropyl group, a 2,2,3,3,3-pentafluoropropyl group, apropyl group, a perfluorobutyl group, a 1,1,2,2,3,3,4,4-octafluorobutylgroup, a butyl group, a perfluoropentyl group, a2,2,3,3,4,4,5,5,5-nonafluoropentyl group, a pentyl group, a hexyl group,a perfluorohexyl group, a heptyl group, a perfluoroheptyl group, anoctyl group and a perfluorooctyl group; a cyclopropylmethyl group, acyclopropyl group, a cyclobutylmethyl group, a cyclopentyl group, acyclohexyl group, a perfluorocyclohexyl group, an adamantyl group, anadamantylmethyl group, an adamantyldimethyl group, a norbornyl group, anorbornylmethyl group, a perfluoroadamantyl group, aperfluoroadamantylmethyl group and the like.

In formula (a4-3), L⁵ is preferably an ethylene group.

The divalent saturated hydrocarbon group of A^(f13) is preferably agroup including a divalent chain hydrocarbon group having 1 to 6 carbonatoms and a divalent alicyclic hydrocarbon group having 3 to 12 carbonatoms, and more preferably a divalent chain hydrocarbon group having 2to 3 carbon atoms.

The saturated hydrocarbon group of A^(f14) is preferably a groupincluding a chain hydrocarbon group having 3 to 12 carbon atoms and analicyclic hydrocarbon group having 3 to 12 carbon atoms, and morepreferably a group including a chain hydrocarbon group having 3 to 10carbon atoms and an alicyclic hydrocarbon group having 3 to 10 carbonatoms. Of these groups, A^(f14) is preferably a group including analicyclic hydrocarbon group having 3 to 12 carbon atoms, and morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group and an adamantyl group.

The structural unit represented by formula (a4-3) includes, for example,structural units represented by formula (a4-1′-1) to formula (a4-1′-11).A structural unit in which a methyl group corresponding to R^(f7) in thestructural unit (a4-3) is substituted with a hydrogen atom is alsoexemplified as the structural unit represented by formula (a4-3).

It is also possible to exemplify, as the structural unit (a4), astructural unit represented by formula (a4-4):

wherein, in formula (a4-4),

R^(f21) represents a hydrogen atom or a methyl group,

A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)—,

j1 to j5 each independently represent an integer of 1 to 6, and

R^(f22) represents a saturated hydrocarbon group having 1 to 10 carbonatoms having a fluorine atom.

Examples of the saturated hydrocarbon group of R^(f22) include thosewhich are the same as the saturated hydrocarbon group represented byR^(a42). R^(f22) is preferably an alkyl group having 1 to 10 carbonatoms having a fluorine atom or an alicyclic hydrocarbon group having 1to 10 carbon atoms having a fluorine atom, more preferably an alkylgroup having 1 to 10 carbon atoms having a fluorine atom, and still morepreferably, an alkyl group having 1 to 6 carbon atoms having a fluorineatom.

In formula (a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferablyan ethylene group or a methylene group, and still more preferably amethylene group.

The structural unit represented by formula (a4-4) includes, for example,the following structural units and structural units in which a methylgroup corresponding to R^(f21) in the structural unit (a4-4) issubstituted with a hydrogen atom in structural units represented by thefollowing formulas.

When the resin (A) includes the structural unit (a4), the content ispreferably 1 to 20 mol %, more preferably 2 to 15 mol %, and still morepreferably 3 to 10 mol %, based on all structural units of the resin (A)

<Structural Unit (a5)>

Examples of a non-leaving hydrocarbon group possessed by the structuralunit (a5) include groups having a linear, branched or cyclic hydrocarbongroup. Of these, the structural unit (a5) is preferably a group havingan alicyclic hydrocarbon group.

The structural unit (a5) includes, for example, a structural unitrepresented by formula (a5-1):

wherein, in formula (a5-1),

R⁵¹ represents a hydrogen atom or a methyl group,

R⁵² represents an alicyclic hydrocarbon group having 3 to 18 carbonatoms, and a hydrogen atom included in the alicyclic hydrocarbon groupmay be substituted with an aliphatic hydrocarbon group having 1 to 8carbon atoms, and

L⁵⁵ represents a single bond or a divalent saturated hydrocarbon grouphaving 1 to 18 carbon atoms, and —CH₂— included in the saturatedhydrocarbon group may be replaced by —O— or —CO—.

The alicyclic hydrocarbon group in R⁵² may be either monocyclic orpolycyclic. The monocyclic alicyclic hydrocarbon group includes, forexample, a cyclopropyl group, a cyclobutyl group, a cyclopentyl groupand a cyclohexyl group. The polycyclic alicyclic hydrocarbon groupincludes, for example, an adamantyl group and a norbornyl group.

The aliphatic hydrocarbon group having 1 to 8 carbon atoms includes, forexample, alkyl groups such as a methyl group, an ethyl group, a propylgroup, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, an octyl group and a2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituentincludes a 3-methyladamantyl group and the like.

R⁵² is preferably an unsubstituted alicyclic hydrocarbon group having 3to 18 carbon atoms, and more preferably an adamantyl group, a norbornylgroup or a cyclohexyl group.

Examples of the divalent saturated hydrocarbon group in L⁵⁵ include adivalent chain saturated hydrocarbon group and a divalent alicyclicsaturated hydrocarbon group, and a divalent chain saturated hydrocarbongroup is preferable.

The divalent chain saturated hydrocarbon group includes, for example,alkanediyl groups such as a methylene group, an ethylene group, apropanediyl group, a butanediyl group and a pentanediyl group.

The divalent alicyclic saturated hydrocarbon group may be eithermonocyclic or polycyclic. Examples of the monocyclic alicyclic saturatedhydrocarbon group include cycloalkanediyl groups such as acyclopentanediyl group and a cyclohexanediyl group. Examples of thepolycyclic divalent alicyclic saturated hydrocarbon group include anadamantanediyl group and a norbornanediyl group.

The group in which —CH₂— included in the divalent saturated hydrocarbongroup represented by L⁵⁵ is replaced by —O— or —CO— includes, forexample, groups represented by formula (L1-) to formula (L1-4). In thefollowing formulas, * and ** each represent a bond, and * represents abond to an oxygen atom.

In formula (L1-1),

X^(x1) represents *—O—CO— or *—CO—O— (* represents a bonding site toL^(x1)),

L^(x1) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 16 carbon atoms,

L^(x2) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 15 carbon atoms, and

the total number of carbon atoms of L^(x1) and L^(x2) is 16 or less.

In formula (L1-2),

L^(x3) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 17 carbon atoms,

L^(x4) represents a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 16 carbon atoms, and

the total number of carbon atoms of L^(x3) and L^(x4) is 17 or less.

In formula (L1-3),

L^(x5) represents a divalent aliphatic saturated hydrocarbon grouphaving 1 to 15 carbon atoms,

L^(x6) and L^(x7) each independently represent a single bond or adivalent aliphatic saturated hydrocarbon group having 1 to 14 carbonatoms, and

the total number of carbon atoms of L^(x5), L^(x6) and L^(x7) is 15 orless.

In formula (L1-4),

L^(x8) and L^(x9) represents a single bond or a divalent aliphaticsaturated hydrocarbon group having 1 to 12 carbon atoms,

W^(x1) represents a divalent alicyclic saturated hydrocarbon grouphaving 3 to 15 carbon atoms, and

the total number of carbon atoms of L^(x8), L^(x9) and W^(x1) is 15 orless.

L^(x1) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x2) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond.

L^(x3) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms.

L^(x4) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x5) is preferably a divalent aliphatic saturated hydrocarbon grouphaving 1 to 8 carbon atoms, and more preferably a methylene group or anethylene group.

L^(x6) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably amethylene group or an ethylene group.

L^(x7) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms.

L^(x8) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

L^(x9) is preferably a single bond or a divalent aliphatic saturatedhydrocarbon group having 1 to 8 carbon atoms, and more preferably asingle bond or a methylene group.

W^(x1) is preferably a divalent alicyclic saturated hydrocarbon grouphaving 3 to 10 carbon atoms, and more preferably a cyclohexanediyl groupor an adamantanediyl group.

The group represented by formula (L1-1) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-2) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-3) includes, for example, thefollowing divalent groups.

The group represented by formula (L1-4) includes, for example, thefollowing divalent groups.

L⁵⁵ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit (a5-1) include the following structuralunits and structural units in which a methyl group corresponding to R⁵¹in the structural unit (a5-1) in the following structural units issubstituted with a hydrogen atom.

When the resin (A) includes the structural unit (a5), the content ispreferably 1 to 30 mol %, more preferably 2 to 20 mol %, and still morepreferably 3 to 15 mol %, based on all structural units of the resin(A).

<Structural Unit (II)>

The resin (A) may further include a structural unit which is decomposedupon exposure to radiation to generate an acid (hereinafter sometimesreferred to as “structural unit (II)). Specific examples of thestructural unit (II) include the structural units mentioned in JP2016-79235 A, and a structural unit having a sulfonate group or acarboxylate group and an organic cation in a side chain or a structuralunit having a sulfonio group and an organic anion in a side chain arepreferable.

The structural unit having a sulfonate group or a carboxylate group in aside chain is preferably a structural unit represented by formula(II-2-A′):

wherein, in formula (II-2-A′),

X^(III3) represents a divalent saturated hydrocarbon group having 1 to18 carbon atoms, —CH₂— included in the saturated hydrocarbon group maybe replaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom, analkyl group having 1 to 6 carbon atoms which may have a halogen atom, ora hydroxy group,

A^(x1) represents an alkanediyl group having 1 to 8 carbon atoms, and ahydrogen atom included in the alkanediyl group may be substituted with afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms,

RA⁻ represents a sulfonate group or a carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

ZA⁺ represents an organic cation.

Examples of the halogen atom represented by R^(III3) include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by R^(III3) include those which are the same asthe alkyl group having 1 to 6 carbon atoms which may have a halogen atomrepresented by R^(a8).

Examples of the alkanediyl group having 1 to 8 carbon atoms representedby A^(x1) include a methylene group, an ethylene group, apropane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, an ethane-1,1-diyl group, apropane-1,1-diyl group, a propane-1,2-diyl group, a propane-2,2-diylgroup, a pentane-2,4-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, a2-methylbutane-1,4-diyl group and the like.

Examples of the perfluoroalkyl group having 1 to 6 carbon atoms whichmay be substituted with A^(X1) include a trifluoromethyl group, aperfluoroethyl group, a perfluoropropyl group, a perfluoroisopropylgroup, a perfluorobutyl group, a perfluorosec-butyl group, aperfluorotert-butyl group, a perfluoropentyl group, a perfluorohexylgroup and the like.

Examples of the divalent saturated hydrocarbon group having 1 to 18carbon atoms represented by X^(III3) include a linear or branchedalkanediyl group, a monocyclic or a polycyclic divalent alicyclicsaturated hydrocarbon group, or a combination thereof.

Specific examples thereof include linear alkanediyl groups such as amethylene group, an ethylene group, a propane-1,3-diyl group, apropane-1,2-diyl group, a butane-1,4-diyl group, a pentane-1,5-diylgroup, a hexane-1,6-diyl group, a heptane-1,7-diyl group, anoctane-1,8-diyl group, a nonane-1,9-diyl group, a decane-1,10-diylgroup, an undecane-1,11-diyl group and a dodecane-1,12-diyl group;branched alkanediyl groups such as a butane-1,3-diyl group, a2-methylpropane-1,3-diyl group, a 2-methylpropane-1,2-diyl group, apentane-1,4-diyl group and a 2-methylbutane-1,4-diyl group;cycloalkanediyl groups such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group and acyclooctane-1,5-diyl group; and divalent polycyclic alicyclic saturatedhydrocarbon groups such as a norbornane-1,4-diyl group, anorbornane-2,5-diyl group, an adamantane-1,5-diyl group and anadamantane-2,6-diyl group.

Those in which —CH₂— included in the saturated hydrocarbon group arereplaced by —O—, —S— or —CO— include, for example, divalent groupsrepresented by formula (X1) to formula (X53). Before replacing —CH₂—included in the saturated hydrocarbon group by —O—, —S— or —CO—, thenumber of carbon atoms is 17 or less. In the following formulas, * and** represent a bonding site, and * represents a bond to A^(x1).

X³ represents a divalent saturated hydrocarbon group having 1 to 16carbon atoms.

X⁴ represents a divalent saturated hydrocarbon group having 1 to 15carbon atoms.

X⁵ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

X⁶ represents a divalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁷ represents a trivalent saturated hydrocarbon group having 1 to 14carbon atoms.

X⁸ represents a divalent saturated hydrocarbon group having 1 to 13carbon atoms.

Examples of ZA⁺ in formula (II-2-A′) include those which are the same asthe cation Z⁺ in the salt (I).

The structural unit represented by formula (II-2-A′) is preferably astructural unit represented by formula (II-2-A):

wherein, in formula (II-2-A), R^(III3), X^(III3) and ZA⁺ are the same asdefined above,

z2A represents an integer of 0 to 6,

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, andwhen z is 2 or more, a plurality of R^(III2) and R^(III4) may be thesame or different form each other, and

Q^(a) and Q^(b) each independently represent a fluorine atom or aperfluoroalkyl group having 1 to 6 carbon atoms.

Examples of the perfluoroalkyl group having 1 to 6 carbon atomsrepresented by R^(III2), R^(III4), Q^(a) and Q^(b) include those whichare the same as the perfluoroalkyl group having 1 to 6 carbon atomsrepresented by Q^(b1).

The structural unit represented by formula (II-2-A) is preferably astructural unit represented by formula (II-2-A-1):

wherein, in formula (II-2-A-1),

R^(III2), R^(III3), R^(III4), Q^(a), Q^(b) and ZA⁺ are the same asdefined above,

R^(III5) represents a saturated hydrocarbon group having 1 to 12 carbonatoms,

z2A1 represents an integer of 0 to 6, and

X^(I2) represents a divalent saturated hydrocarbon group having 1 to 11carbon atoms, —CH₂— included in the saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—, and a hydrogen atom included in thesaturated hydrocarbon group may be substituted with a halogen atom or ahydroxy group.

Examples of the saturated hydrocarbon group having 1 to 12 carbon atomsrepresented by R^(III5) include linear or branched alkyl groups such asa methyl group, an ethyl group, a propyl group, an isopropyl group, abutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group, a decylgroup, an undecyl group and a dodecyl group.

Examples of the divalent saturated hydrocarbon group represented byX^(I2) include those which are the same as the divalent saturatedhydrocarbon group represented by X^(III3).

The structural unit represented by formula (II-2-A-1) is more preferablya structural unit represented by formula (II-2-A-2):

wherein, in formula (II-2-A-2), R^(III3), R^(III5) and ZA⁺ are the sameas defined above, and

m and n each independently represent 1 or 2.

The structural unit represented by formula (II-2-A′) includes, forexample, the following structural units and the structural unitsmentioned in WO 2012/050015 A. ZA⁺ represents an organic cation.

The structural unit having a sulfonio group and an organic anion in aside chain is preferably a structural unit represented by formula(II-1-1):

wherein, in formula (II-1-1),

A^(II1) represents a single bond or a divalent linking group,

R^(II1) represents a divalent aromatic hydrocarbon group having 6 to 18carbon atoms,

R^(II2) and R^(II3) each independently represent a hydrocarbon grouphaving 1 to 18 carbon atoms, and R^(II2) and R^(II3) may be bonded toeach other to form a ring together with sulfur atoms to which R^(II2)and R^(II3) are bonded,

R^(II4) represents a hydrogen atom, a halogen atom or an alkyl grouphaving 1 to 6 carbon atoms which may have a halogen atom, and

A⁻ represents an organic anion.

Examples of the divalent aromatic hydrocarbon group having 6 to 18carbon atoms represented by R^(II1) include a phenylene group and anaphthylene group.

Examples of the hydrocarbon group represented by R^(II2) and R^(II3)include an alkyl group, an alicyclic hydrocarbon group, an aromatichydrocarbon group and groups obtained by combining these groups, andspecifically include those which are the same as mentioned in R^(a1′),R^(a2′) and R^(a3′).

Examples of the halogen atom represented by R^(II4) include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom.

Examples of the alkyl group having 1 to 6 carbon atoms which may have ahalogen atom represented by R^(II4) include those which are the same asthe alkyl group having 1 to 6 carbon atoms which may have a halogen atomrepresented by R^(a8).

Examples of the divalent linking group represented by A^(II1) include adivalent saturated hydrocarbon group having 1 to 18 carbon atoms, and—CH₂— included in the divalent saturated hydrocarbon group may bereplaced by —O—, —S— or —CO—. Specific examples thereof include thosewhich are the same as the divalent saturated hydrocarbon group having 1to 18 carbon atoms represented by X^(III3).

Examples of the structural unit including a cation in formula (II-1-1)include the following structural units.

Examples of the organic anion represented by A⁻ include a sulfonic acidanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxylicacid anion. The organic anion represented by A⁻ is preferably a sulfonicacid, and the sulfonic acid anion is preferably an anion included in theabove-mentioned salt represented by formula (B1).

Examples of the sulfonylimide anion represented by A⁻ include thefollowing.

Examples of the sulfonylmethide anion include the following.

Examples of the carboxylic acid anion include the following.

Examples of the structural unit represented by formula (II-1-1) includestructural units represented by the following formulas.

When the structural unit (II) is included in the resin (A), the contentof the structural unit (II) is preferably 1 to 20 mol %, more preferably2 to 15 mol %, and still more preferably 3 to 10 mol %, based on allstructural units of the resin (A).

The resin (A) may include structural units other than the structuralunits mentioned above, and examples of such structural unit includestructural units well-known in the art.

The resin (A) is preferably a resin composed of a structural unit (a1)and a structural unit (s), i.e., a copolymer of a monomer (a1) and amonomer (s).

The structural unit (a1) is preferably at least one selected from thegroup consisting of a structural unit (a1-0), a structural unit (a1-1)and a structural unit (a1-2) (preferably the structural unit having acyclohexyl group, and a cyclopentyl group), more preferably at leasttwo, and still more preferably at least two selected from the groupconsisting of a structural unit (a1-1) and a structural unit (a1-2).

The structural unit (s) is preferably at least one selected from thegroup consisting of a structural unit (a2) and a structural unit (a3).The structural unit (a2) is preferably a structural unit (a2-1) or astructural unit (a2-A). The structural unit (a3) is preferably at leastone selected from the group consisting of a structural unit representedby formula (a3-1), a structural unit represented by formula (a3-2) and astructural unit represented by formula (a3-4).

The respective structural units constituting the resin (A) may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g. radical polymerizationmethod). The content of the respective structural units included in theresin (A) can be adjusted according to the amount of the monomer used inthe polymerization.

The weight-average molecular weight of the resin (A) is preferably 2,000or more (more preferably 2,500 or more, and still more preferably 3,000or more), and 50,000 or less (more preferably 30,000 or less, and stillmore preferably 15,000 or less). As used herein, the weight-averagemolecular weight is a value determined by gel permeation chromatographyunder the conditions mentioned in Examples.

<Resin Other than Resin (A)>

In the resist composition of the present invention, the resin other thanthe resin (A) may be used in combination.

The resin other than the resin (A) includes, for example, a resinincluding a structural unit (a4) or a structural unit (a5) (hereinaftersometimes referred to as resin (X)).

The resin (X) is preferably a resin including a structural unit (a4),particularly.

In the resin (X), the content of the structural unit (a4) is preferably30 mol % or more, more preferably 40 mol % or more, and still morepreferably 45 mol % or more, based on the total of all structural unitsof the resin (X).

Examples of the structural unit, which may be further included in theresin (X), include a structural unit (a1), a structural unit (a2), astructural unit (a3) and structural units derived from other knownmonomers. Particularly, the resin (X) is preferably a resin composedonly of a structural unit (a4) and/or a structural unit (a5).

The respective structural unit constituting the resin (X) may be usedalone, or two or more structural units may be used in combination. Usinga monomer from which these structural units are derived, it is possibleto produce by a known polymerization method (e.g. radical polymerizationmethod). The content of the respective structural units included in theresin (X) can be adjusted according to the amount of the monomer used inthe polymerization.

The weight-average molecular weight of the resin (X) is preferably 6,000or more (more preferably 7,000 or more) and 80,000 or less (morepreferably 60,000 or less). The measurement means of the weight-averagemolecular weight of the resin (X) is the same as in the case of theresin (A).

When the resist composition of the present invention includes the resin(X), the content is preferably 1 to 60 parts by mass, more preferably 1to 50 parts by mass, still more preferably 1 to 40 parts by mass,particularly preferably 1 to 30 parts by mass, and particularlypreferably 1 to 8 parts by mass, based on 100 parts by mass of the resin(A).

The content of the resin (A) in the resist composition is preferably 80%by mass or more and 99% by mass or less, and more preferably 90% by massor more and 99% by mass or less, based on the solid component of theresist composition. When including resins other than the resin (A), thetotal content of the resin (A) and resins other than the resin (A) ispreferably 80% by mass or more and 99% by mass or less, and morepreferably 90% by mass or more and 99% by mass or less, based on thesolid component of the resist composition. As used herein, “solidcomponent of the resist composition” means the total amount ofcomponents obtained by removing a solvent (E) mentioned later from thetotal amount of the resist composition. The solid component of theresist composition and the content of the resin thereto can be measuredby a known analysis means such as liquid chromatography or gaschromatography.

<Solvent (E)>

The content of the solvent (E) in the resist composition is usually 90%by mass or more and 99.9% by mass or less, preferably 92% by mass ormore and 99% by mass or less, and more preferably 94% by mass or moreand 99% by mass or less. The content of the solvent (E) can be measured,for example, by a known analysis means such as liquid chromatography orgas chromatography.

Examples of the solvent (E) include glycol ether esters such asethylcellosolve acetate, methylcellosolve acetate and propylene glycolmonomethyl ether acetate; glycol ethers such as propylene glycolmonomethyl ether; esters such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; ketones such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and cyclic esters such asγ-butyrolactone. The solvent (E) may be used alone, or two or moresolvents may be used.

<Quencher (C)>

Examples of the quencher (C) include a basic nitrogen-containing organiccompound, and a salt generating an acid having an acidity lower thanthat of an acid generated from an acid generator (B). The content of thequencher (C) is preferably about 0.01 to 5% by mass, and more preferablyabout 0.01 to 3% by mass based on the amount of the solid component ofthe resist composition.

Examples of the basic nitrogen-containing organic compound include amineand an ammonium salt. Examples of the amine include an aliphatic amineand an aromatic amine. Examples of the aliphatic amine include a primaryamine, a secondary amine and a tertiary amine.

Examples of the amine include 1-naphthylamine, 2-naphthylamine, aniline,diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,dipentylamine, dihexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, triethylamine, trimethylamine, tripropylamine,tributylamine, tripentylamine, trihexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, methyldibutylamine,methyldipentylamine, methyldihexylamine, methyldicyclohexylamine,methyldiheptylamine, methyldioctylamine, methyldinonylamine,methyldidecylamine, ethyldibutylamine, ethyldipentylamine,ethyldihexylamine, ethyldiheptylamine, ethyldioctylamine,ethyldinonylamine, ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, 2,2′-methylenebisaniline,imidazole, 4-methylimidazole, pyridine, 4-methylpyridine,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene,1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy)ethane,di(2-pyridyl)ketone, 4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide,2,2′-dipyridylamine, 2,2′-dipicolylamine, bipyridine and the like,preferably aromatic amines such as diisopropylaniline, and morepreferably 2,6-diisopropylaniline.

Examples of the ammonium salt include tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,3-(trifluoromethyl)phenyltrimethylammonium hydroxide,tetra-n-butylammonium salicylate and choline.

The acidity in a salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) is indicated bythe acid dissociation constant (pKa). Regarding the salt generating anacid having an acidity lower than that of an acid generated from theacid generator (B), the acid dissociation constant of an acid generatedfrom the salt usually meets the following inequality: −3<pKa, preferably−1<pKa<7, and more preferably 0<pKa<5.

Examples of the salt generating an acid having an acidity lower thanthat of an acid generated from the acid generator (B) include saltsrepresented by the following formulas, a salt represented by formula (D)mentioned in JP 2015-147926 A (hereinafter sometimes referred to as“weak acid inner salt (D)”, and salts mentioned in JP 2012-229206 A, JP2012-6908 A, JP 2012-72109 A, JP 2011-39502 A and JP 2011-191745 A. Thesalt generating an acid having an acidity lower than that of an acidgenerated from the acid generator (B) is preferably a weak acid innersalt (D).

Examples of the weak acid inner salt (D) include the following salts.

<Other Components>

The resist composition of the present invention may also includecomponents other than the components mentioned above (hereinaftersometimes referred to as “other components (F)”). The other components(F) are not particularly limited and it is possible to use variousadditives known in the resist field, for example, sensitizers,dissolution inhibitors, surfactants, stabilizers and dyes.

<Preparation of Resist Composition>

The resist composition of the present invention can be prepared bymixing a salt (I) and a resin (A), and if necessary, an acid generator(B), resins other than the resin (A), a solvent (E), a quencher (C) andother components (F). The order of mixing these components is any orderand is not particularly limited. It is possible to select, as thetemperature during mixing, appropriate temperature from 10 to 40° C.,according to the type of the resin, the solubility in the solvent (E) ofthe resin and the like. It is possible to select, as the mixing time,appropriate time from 0.5 to 24 hours according to the mixingtemperature. The mixing means is not particularly limited and it ispossible to use mixing with stirring.

After mixing the respective components, the mixture is preferablyfiltered through a filter having a pore diameter of about 0.003 to 0.2μm.

(Method for Producing Resist Pattern)

The method for producing a resist pattern of the present inventioninclude:

(1) a step of applying the resist composition of the present inventionon a substrate,(2) a step of drying the applied composition to form a compositionlayer,(3) a step of exposing the composition layer,(4) a step of heating the exposed composition layer, and(5) a step of developing the heated composition layer.

The resist composition can be usually applied on a substrate using aconventionally used apparatus, such as a spin coater. Examples of thesubstrate include inorganic substrates such as a silicon wafer. Beforeapplying the resist composition, the substrate may be washed, and anorganic antireflection film may be formed on the substrate.

The solvent is removed by drying the applied composition to form acomposition layer. Drying is performed by evaporating the solvent usinga heating device such as a hot plate (so-called “prebake”), or adecompression device. The heating temperature is preferably 50 to 200°C. and the heating time is preferably 10 to 180 seconds. The pressureduring drying under reduced pressure is preferably about 1 to 1.0×10⁵Pa.

The composition layer thus obtained is usually exposed using an aligner.The aligner may be a liquid immersion aligner. It is possible to use, asan exposure source, various exposure sources, for example, exposuresources capable of emitting laser beam in an ultraviolet region such asKrF excimer laser (wavelength of 248 nm), ArF excimer laser (wavelengthof 193 nm) and F₂ excimer laser (wavelength of 157 nm), an exposuresource capable of emitting harmonic laser beam in a far-ultraviolet orvacuum ultra violet region by wavelength-converting laser beam from asolid-state laser source (YAG or semiconductor laser), an exposuresource capable of emitting electron beam or EUV and the like. As usedherein, such exposure to radiation is sometimes collectively referred toas “exposure”. The exposure is usually performed through a maskcorresponding to a pattern to be required. When electron beam is used asthe exposure source, exposure may be performed by direct writing withoutusing the mask.

The exposed composition layer is subjected to a heat treatment(so-called “post-exposure bake”) to promote the deprotection reaction inan acid-labile group. The heating temperature is usually about 50 to200° C., and preferably about 70 to 150° C.

The heated composition layer is usually developed with a developingsolution using a development apparatus. Examples of the developingmethod include a dipping method, a paddle method, a spraying method, adynamic dispensing method and the like. The developing temperature ispreferably, for example, 5 to 60° C. and the developing time ispreferably, for example, 5 to 300 seconds. It is possible to produce apositive resist pattern or negative resist pattern by selecting the typeof the developing solution as follows.

When the positive resist pattern is produced from the resist compositionof the present invention, an alkaline developing solution is used as thedeveloping solution. The alkaline developing solution may be variousaqueous alkaline solutions used in this field. Examples thereof includeaqueous solutions of tetramethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as choline).The surfactant may be contained in the alkaline developing solution.

It is preferable that the developed resist pattern is washed withultrapure water and then water remaining on the substrate and thepattern is removed.

When the negative resist pattern is produced from the resist compositionof the present invention, a developing solution containing an organicsolvent (hereinafter sometimes referred to as “organic developingsolution”) is used as the developing solution.

Examples of the organic solvent contained in the organic developingsolution include ketone solvents such as 2-hexanone and 2-heptanone;glycol ether ester solvents such as propylene glycol monomethyl etheracetate; ester solvents such as butyl acetate; glycol ether solventssuch as propylene glycol monomethyl ether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of the organic solvent in the organic developing solution ispreferably 90% by mass or more and 100% by mass or less, more preferably95% by mass or more and 100% by mass or less, and still more preferablythe organic developing solution is substantially composed of the organicsolvent.

Particularly, the organic developing solution is preferably a developingsolution containing butyl acetate and/or 2-heptanone. The total contentof butyl acetate and 2-heptanone in the organic developing solution ispreferably 50% by mass or more and 100% by mass or less, more preferably90% by mass or more and 100% by mass or less, and still more preferablythe organic developing solution is substantially composed of butylacetate and/or 2-heptanone.

The surfactant may be contained in the organic developing solution. Atrace amount of water may be contained in the organic developingsolution.

During development, the development may be stopped by replacing by asolvent with the type different from that of the organic developingsolution.

The developed resist pattern is preferably washed with a rinsingsolution. The rinsing solution is not particularly limited as long as itdoes not dissolve the resist pattern, and it is possible to use asolution containing an ordinary organic solvent which is preferably analcohol solvent or an ester solvent.

After washing, the rinsing solution remaining on the substrate and thepattern is preferably removed.

(Application)

The resist composition of the present invention is suitable as a resistcomposition for exposure of KrF excimer laser, a resist composition forexposure of ArF excimer laser, a resist composition for exposure ofelectron beam (EB) or a resist composition for exposure of EUV,particularly a resist composition for exposure of ArF excimer laser, aresist composition for exposure of electron beam (EB) or a resistcomposition for exposure of EUV, and the resist composition is usefulfor fine processing of semiconductors.

EXAMPLES

The present invention will be described more specifically by way ofExamples. Percentages and parts expressing the contents or amounts usedin the Examples are by mass unless otherwise specified.

The weight-average molecular weight is a value determined by gelpermeation chromatography. Analysis conditions of gel permeationchromatography are as follows.

Column: TSKgel Multipore IIXL-M×3+guardcolumn (manufactured by TOSOHCORPORATION)

Eluent: tetrahydrofuran

Flow rate: 1.0 mL/min

Detector: RI detector

Column temperature: 40° C.

Injection amount: 100 μl

Molecular weight standards: polystyrene standard (manufactured by TOSOHCORPORATION)

Structures of compounds were confirmed by measuring a molecular ion peakusing mass spectrometry (Liquid Chromatography: Model 1100, manufacturedby Agilent Technologies, Inc., Mass Spectrometry: Model LC/MSD,manufactured by Agilent Technologies, Inc.). The value of this molecularion peak in the following Examples is indicated by “MASS”.

Example 1: Synthesis of Salt Represented by Formula (I-1)

10 Parts of a salt represented by formula (I-1-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 4.93 parts of a compoundrepresented by formula (I-1-c) was added, followed by stirring at 50° C.for 3 hours and further cooling to 23° C. To the mixture thus obtained,70 parts of chloroform and 20 parts of an aqueous 5% oxalic acidsolution were added, and after stirring at 23° C. for 30 minutes, theorganic layer was isolated through separation. To the organic layer thusobtained, 20 parts of ion-exchanged water was added, and after stirringat 23° C. for 30 minutes, the organic layer was isolated throughseparation. This water washing operation was repeated five times. Theorganic layer thus obtained was concentrated and then 25 parts ofacetonitrile and 100 parts of tert-butyl methyl ether were added to theconcentrated residue, followed by stirring at 23° C. for 30 minutes,removal of the supernatant and further concentration. To theconcentrated residue thus obtained, 50 parts of n-heptane was added,followed by stirring at 23° C. for 30 minutes and further filtration toobtain 9.85 parts of a salt represented by formula (I-1).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 353.1

Example 2: Synthesis of Salt Represented by Formula (I-141)

9.41 Parts of a salt represented by formula (I-141-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 4.93 parts of a compoundrepresented by formula (I-1-c) was added, followed by stirring at 50° C.for 3 hours and further cooling to 23° C. To the mixture thus obtained,70 parts of chloroform and 20 parts of an aqueous 5% oxalic acidsolution were added, and after stirring at 23° C. for 30 minutes, theorganic layer was isolated through separation. To the organic layer thusobtained, 20 parts of ion-exchanged water was added, and after stirringat 23° C. for 30 minutes, the organic layer was isolated throughseparation. This water washing operation was repeated five times. Theorganic layer thus obtained was concentrated and then 15 parts ofacetonitrile and 100 parts of tert-butyl methyl ether were added to theconcentrated residue, followed by stirring at 23° C. for 30 minutes,removal of the supernatant and further concentration. To theconcentrated residue thus obtained, 50 parts of n-heptane was added,followed by stirring at 23° C. for 30 minutes and further filtration toobtain 6.89 parts of a salt represented by formula (I-141).

MASS (ESI (+) Spectrum): M⁺ 237.1

MASS (ESI (−) Spectrum): M⁻ 353.1

Example 3: Synthesis of Salt Represented by Formula (I-14)

9.54 Parts of a salt represented by formula (I-14-a) and 30 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 2.68 parts of a compound representedby formula (I-1-c) was added, followed by stirring at 23° C. for 8hours. To the mixture thus obtained, 30 parts of ion-exchanged water wasadded, and after stirring at 23° C. for 30 minutes, the organic layerwas isolated through separation. To the organic layer thus obtained, 20parts of an aqueous 5% oxalic acid solution was added, and afterstirring at 23° C. for 30 minutes, the organic layer was isolatedthrough separation. To the organic layer thus obtained, 30 parts ofion-exchanged water was added, and after stirring at 23° C. for 30minutes, the organic layer was isolated through separation. This waterwashing operation was repeated five times. The organic layer thusobtained was concentrated and then 3 parts of acetonitrile and 30 partsof tert-butyl methyl ether were added to the concentrated residue,followed by stirring at 23° C. for 30 minutes, removal of thesupernatant and further concentration to obtain 7.88 parts of a saltrepresented by formula (I-14).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 561.2

Example 4: Synthesis of Salt Represented by Formula (I-16)

10 Parts of a salt represented by formula (I-1-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 4.63 parts of a compoundrepresented by formula (I-16-c) was added, followed by stirring at 50°C. for 3 hours and further cooling to 23° C. To the mixture thusobtained, 70 parts of chloroform and 20 parts of an aqueous 5% oxalicacid solution were added, and after stirring at 23° C. for 30 minutes,the organic layer was isolated through separation. To the organic layerthus obtained, 20 parts of ion-exchanged water was added, and afterstirring at 23° C. for 30 minutes, the organic layer was isolatedthrough separation. This water washing operation was repeated fivetimes. The organic layer thus obtained was concentrated and then 10parts of acetonitrile and 90 parts of tert-butyl methyl ether were addedto the concentrated residue, followed by stirring at 23° C. for 30minutes, removal of the supernatant and further concentration to obtain7.66 parts of a salt represented by formula (I-16).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 341.0

Example 5: Synthesis of Salt Represented by Formula (I-18)

10 Parts of a salt represented by formula (I-1-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 5.53 parts of a compoundrepresented by formula (I-18-c) was added, followed by stirring at 50°C. for 3 hours and further cooling to 23° C. To the mixture thusobtained, 70 parts of chloroform and 20 parts of an aqueous 5% oxalicacid solution were added, and after stirring at 23° C. for 30 minutes,the organic layer was isolated through separation. To the organic layerthus obtained, 20 parts of ion-exchanged water was added, and afterstirring at 23° C. for 30 minutes, the organic layer was isolatedthrough separation. This water washing operation was repeated fivetimes. The organic layer thus obtained was concentrated and then 10parts of acetonitrile and 90 parts of tert-butyl methyl ether were addedto the concentrated residue, followed by stirring at 23° C. for 30minutes, removal of the supernatant and further concentration to obtain7.29 parts of a salt represented by formula (I-18).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 377.0

Example 6: Synthesis of Salt Represented by Formula (I-11)

9.68 Parts of a salt represented by formula (I-11-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 4.93 parts of a compoundrepresented by formula (I-1-c) was added, followed by stirring at 50° C.for 3 hours and further cooling to 23° C. To the mixture thus obtained,70 parts of chloroform and 20 parts of an aqueous 5% oxalic acidsolution were added, and after stirring at 23° C. for 30 minutes, theorganic layer was isolated through separation. To the organic layer thusobtained, 20 parts of ion-exchanged water was added, and after stirringat 23° C. for 30 minutes, the organic layer was isolated throughseparation. This water washing operation was repeated five times. Theorganic layer thus obtained was concentrated and then 30 parts oftert-butyl methyl ether was added to the concentrated residue, followedby stirring at 23° C. for 30 minutes, removal of the supernatant andfurther concentration. To the concentrated residue thus obtained, 30parts of n-heptane was added, followed by stirring at 23° C. for 30minutes and further filtration to obtain 7.77 parts of a saltrepresented by formula (I-11).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 383.1

Example 7: Synthesis of Salt Represented by Formula (I-13)

9.13 Parts of a salt represented by formula (I-13-a) and 30 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 2.68 parts of a compound representedby formula (I-1-c) was added, followed by stirring at 23° C. for 8hours. To the mixture thus obtained, 30 parts of ion-exchanged water wasadded, and after stirring at 23° C. for 30 minutes, the organic layerwas isolated through separation. To the organic layer thus obtained, 20parts of an aqueous 5% oxalic acid solution was added, and afterstirring at 23° C. for 30 minutes, the organic layer was isolatedthrough separation. To the organic layer thus obtained, 30 parts ofion-exchanged water was added, and after stirring at 23° C. for 30minutes, the organic layer was isolated through separation. This waterwashing operation was repeated five times. The organic layer thusobtained was concentrated and then 30 parts of tert-butyl methyl etherwas added to the concentrated residue, followed by stirring at 23° C.for 30 minutes, removal of the supernatant and further concentration toobtain 6.42 parts of a salt represented by formula (I-13).

MASS (ESI (+) Spectrum): M⁺ 263.1

MASS (ESI (−) Spectrum): M⁻ 531.2

Example 8: Synthesis of Salt Represented by Formula (I-138)

11.23 Parts of a salt represented by formula (I-138-a) and 20 parts ofchloroform were mixed, followed by stirring at 23° C. for 30 minutes. Tothe mixed solution thus obtained, 3.88 parts of a compound representedby formula (I-1-b) was added, followed by stirring at 50° C. for 2hours. To the mixed solution thus obtained, 5.53 parts of a compoundrepresented by formula (I-18-c) was added, followed by stirring at 50°C. for 3 hours and further cooling to 23° C. To the mixture thusobtained, 70 parts of chloroform and 20 parts of an aqueous 5% oxalicacid solution were added, and after stirring at 23° C. for 30 minutes,the organic layer was isolated through separation. To the organic layerthus obtained, 20 parts of ion-exchanged water was added, and afterstirring at 23° C. for 30 minutes, the organic layer was isolatedthrough separation. This water washing operation was repeated fivetimes. The organic layer thus obtained was concentrated and then 10parts of acetonitrile and 90 parts of tert-butyl methyl ether were addedto the concentrated residue, followed by stirring at 23° C. for 30minutes, removal of the supernatant and further concentration to obtain7.11 parts of a salt represented by formula (I-138).

MASS (ESI (+) Spectrum): M⁺ 317.1

MASS (ESI (−) Spectrum): M⁻ 377.0

Synthesis of Resin

Compounds (monomers) used in synthesis of a resin (A) are shown below.Hereinafter, these compounds are referred to as “monomer (a1-1-3)”according to the formula number.

Synthesis Example 1: Synthesis of Resin A1

Using a monomer (a1-1-3), a monomer (a1-2-5), a monomer (a2-1-1) and amonomer (a3-1-1) as monomers, these monomers were mixed in a molar ratioof 14:45:2.5:38.5 [monomer (a1-1-3):monomer (a1-2-5):monomer(a2-1-1):monomer (a3-1-1)], and propylene glycol monomethyl etheracetate was added in the amount of 1.5 mass times the total mass of allmonomers to obtain a solution. To this solution, azobisisobutyronitrileand azobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 1 mol % and 3 mol % based on the total molar number of allmonomers, followed by heating at 73° C. for about 5 hours. The reactionmixture thus obtained was poured into a large amount of a methanol/watermixed solvent to precipitate a resin, and this resin was filtered. Afterperforming a reprecipitation operation in which a solution obtained bydissolving again the resin thus obtained in propylene glycol monomethylether acetate is poured into a methanol/water mixed solvent toprecipitate the resin, followed by filtration of this resin, twice, aresin A1 having a weight-average molecular weight of 7.9×10³ in a yieldof 88%. This resin A1 includes the following structural unit.

Synthesis Example 2: Synthesis of Resin X1

Using a monomer (a4-1-4) as a monomer, methyl isobutyl ketone was addedin the amount of 1.5 mass times the total mass of all monomers to obtaina solution. To this solution, azobisisobutyronitrile andazobis(2,4-dimethylvaleronitrile) as initiators were added in theamounts of 0.7 mol % and 2.1 mol % based on the total molar number ofall monomers, followed by heating at 75° C. for about 5 hours. Thereaction mixture thus obtained was poured into a large amount of amethanol/water mixed solvent to precipitate a resin, and this resin wasfiltered to obtain a resin X1 having a weight-average molecular weightof 1.7×10⁴ in a yield of 77%. This resin X1 includes the followingstructural unit.

Synthesis Example 3 [Synthesis of Resin A3]

Using a monomer (a1-4-2), a monomer (a1-1-3) and a monomer (a1-2-6) asmonomers, these monomers were mixed in a molar ratio of 38:24:38[monomer (a1-4-2):monomer (a1-1-3):monomer (a1-2-6)], methyl isobutylketone was added in the amount of 1.5 mass times the total mass of allmonomers. To the mixture thus obtained, azobisisobutyronitrile as aninitiator was added in the amount of 7 mol % based on the total molarnumber of all monomers, and the polymerization was performed by heatingat 85° C. for about 5 hours. To the polymerization reaction solution, anaqueous p-toluenesulfonic acid solution was added, followed by stirringfor 6 hours and further isolation through separation. The organic layerthus recovered was poured into a large amount of n-heptane toprecipitate a resin, which was filtered and recovered to obtain a resinA3 (copolymer) having a weight-average molecular weight of about 5.3×10³in a yield of 78%. This resin A3 includes the following structural unit.

<Preparation of Resist Composition>

As shown in Table 7, the following components were mixed and the mixturethus obtained was filtered through a fluororesin filter having a porediameter of 0.2 μm to prepare resist compositions.

TABLE 7 Resist Acid composition Resin generator Salt (I) Quencher (C)PB/PEB Composition 1 X1/A1 = — I-1 = D1 = 90° C./85° C. 0.2/10 parts 0.9parts 0.28 parts Composition 2 X1/A1 = — I-141 = D1 = 90° C./85° C.0.2/10 parts 0.9 parts 0.28 parts Composition 3 X1/A1 = — I-14 = D1 =90° C./85° C. 0.2/10 parts 0.9 parts 0.28 parts Composition 4 X1/A1 = —I-141 = D1 = 90° C./85° C. 0.2/10 parts 1.4 parts 0.28 parts Composition5 X1/A1 = — I-11 = D1 = 90° C./85° C. 0.2/10 parts 0.9 parts 0.28 partsComposition 6 X1/A1 = — I-13 = D1 = 90° C./85° C. 0.2/10 parts 0.9 parts0.28 parts Comparative X1/A1 = IX-1 = — D1 = 90° C./85° C. Composition 10.2/10 parts 0.9 parts 0.28 parts Comparative X1/A1 = IX-2 = — D1 = 90°C./85° C. Composition 2 0.2/10 parts 0.9 parts 0.28 parts

<Resin>

A1, X1: Resin A1, Resin X1

<Salt (I)>

I-1: Salt represented by formula (I-1)

I-11: Salt represented by formula (I-11)

I-13: Salt represented by formula (I-13)

I-14: Salt represented by formula (I-14)

I-141: Salt represented by formula (I-141)

<Acid Generator>

IX-1: Salt represented by formula (IX-1) (synthesized in accordance withExamples of JP 2007-161707 A)

IX-2: Salt represented by formula (IX-2) (synthesized in accordance withExamples of JP 2007-145824 A)

<Quencher (C)>

D1: (manufactured by Tokyo Chemical Industry Co., Ltd.)

<Solvent>

Propylene glycol monomethyl ether acetate 265 parts  Propylene glycolmonomethyl ether 20 parts 2-Heptanone 20 parts γ-Butyrolactone 3.5parts 

<Production of Resist Pattern and Evaluation Thereof>

A composition for an organic antireflective film (ARC-29, manufacturedby Nissan Chemical Co. Ltd.) was applied onto a silicon wafer and bakedunder the conditions at 205° C. for 60 seconds to form a 78 nm thickorganic antireflective film on the silicon wafer, and then the aboveresist composition was applied thereon by coating (spin coating) in sucha manner that the thickness of the film after drying became 160 nm. Thesilicon wafer coated with the resist composition was pre-baked for 60seconds on a direct hot plate at the temperature mentioned in the “PB”column in Table 7 to form a composition layer. The silicon wafer withthe composition layer thus formed thereon was exposed through a mask forforming a line-and-space pattern (line-and-space pitch of 180 nm/line of104 nm) stepwise with changing exposure dose using an ArF excimer laserstepper for immersion lithography (XT:1900Gi, manufactured by ASML Ltd.:NA=1.35, 3/4 Annular, XY-polarization). Ultrapure water was used formedium of immersion.

After exposure, post-exposure baking was performed on a hot plate for 60seconds at the temperature mentioned in the “PEB” column in Table 7.Then, the composition layer on the silicon wafer was subjected to paddledevelopment at 23° C. for 60 seconds using an aqueous 2.38% by masstetramethylammonium hydroxide solution as a developing solution toobtain a resist pattern.

Effective sensitivity was represented as the exposure dose at which aline pattern with a width of 80 nm was obtained in the resist patternthus obtained.

(Evaluation of Line Edge Roughness (LER))

A roughness width of irregularities in each wall surface of the obtainedresist pattern was observed using a scanning electron microscope. Thisroughness width was shown in Table 8 as LER (nm).

TABLE 8 Resist composition LER (nm) Example 9 Composition 1 4.74 Example10 Composition 2 4.68 Example 11 Composition 3 4.63 Example 12Composition 4 4.60 Example 13 Composition 5 4.71 Example 14 Composition6 4.61 Comparative Example 1 Comparative Composition 1 5.06 ComparativeExample 2 Comparative Composition 2 5.08

As compared with Comparative Compositions 1 and 2, Compositions 1 to 6exhibited small roughness width of the irregularity in wall surface of aresist pattern, thus leading to satisfactory evaluation of the line edgeroughness.

<Preparation of Resist Composition>

As shown in Table 9, the following components were mixed and the mixturethus obtained was filtered through a fluororesin filter having a porediameter of 0.2 μm to prepare resist compositions.

TABLE 9 Resist Acid Salt Quencher composition Resin generator (I) (C)PB/PEB Composition 7 A3 = — I-16 = C1 = 100° C./ 10 parts 1.5 parts 0.35parts 130° C. Composition 8 A3 = — I-18 = C1 = 100° C./ 10 parts 1.5parts 0.35 parts 130° C. Composition 9 A3 = — I-138 = C1 = 100° C./ 10parts 1.5 parts 0.35 parts 130° C. Comparative A3 = IX-3 = — C1 = 100°C./ Composition 3 10 parts 1.5 parts 0.35 parts 130° C. Comparative A3 =IX-4 = — C1 = 100° C./ Composition 4 10 parts 1.5 parts 0.35 parts 130°C.

<Resin>

A3: Resin A3

<Salt (I)>

I-16: Salt represented by formula (I-16)

I-18: Salt represented by formula (I-18)

I-138: Salt represented by formula (I-138)

<Acid Generator>

IX-3: Salt represented by formula (IX-3) (synthesized with reference toExamples of JP 2010-039146 A)

IX-4: Salt represented by formula (IX-4) (synthesized with reference toExamples of JP 2010-039476 A)

<Quencher (C)>

C1: synthesized by the method mentioned in JP 2011-39502 A

<Solvent (E)>

Propylene glycol monomethyl ether acetate 400 parts Propylene glycolmonomethyl ether 100 parts γ-Butyrolactone  5 parts(Evaluation of Exposure of Resist Composition with Electron Beam)

Each 6 inch-diameter silicon wafer was treated with hexamethyldisilazaneand then baked on a direct hot plate at 90° C. for 60 seconds. A resistcomposition was spin-coated on the silicon wafer in such a manner thatthe thickness of the composition later became 0.04 μm. The coatedsilicon wafer was prebaked on the direct hot plate at the temperatureshown in the column “PB” of Table 9 for 60 seconds. Using anelectron-beam direct-write system (“ELS-F125 125 keV”, manufactured byELIONIX INC.), line-and-space patterns (pitch of 60 nm/line width of 30nm) were directly written on the composition layer formed on the waferwhile changing the exposure dose stepwise.

After the exposure, post-exposure baking was performed on the hot plateat the temperature shown in the column “PEB” of Table 9 for 60 seconds,followed by paddle development with an aqueous 2.38% by masstetramethylammonium hydroxide solution for 60 seconds to obtain a resistpattern.

The resist pattern (line-and-space pattern) thus obtained was observedby a scanning electron microscope and effective sensitivity was definedas the exposure dose at which a ratio of a line width to a space patternof a line-and-space pattern with a pitch of 60 nm became 1:1 wasobtained.

Evaluation of Line Edge Roughness (LER): Line edge roughness wasdetermined by measuring a roughness width of the irregularity in wallsurface of a resist pattern produced by the effective sensitivity usinga scanning electron microscope. The results are shown in Table 10.

TABLE 10 Resist composition LER Example 15 Composition 7 3.82 Example 16Composition 8 3.64 Example 17 Composition 9 3.58 Comparative Example 3Comparative Composition 3 4.18 Comparative Example 4 ComparativeComposition 4 4.21

As compared with Comparative Compositions 3 and 4, Compositions 7 to 9exhibited small roughness width of the irregularity in wall surface of aresist pattern, thus leading to satisfactory evaluation of the line edgeroughness.

INDUSTRIAL APPLICABILITY

A salt and a resist composition including the salt of the presentinvention exhibit satisfactory line edge roughness and are useful forfine processing of semiconductors.

1. A salt represented by formula (I):

wherein, in formula (I), Q¹ and Q² each independently represent afluorine atom or a perfluoroalkyl group having 1 to 6 carbon atoms, R¹and R² each independently represent a hydrogen atom, a fluorine atom ora perfluoroalkyl group having 1 to 6 carbon atoms, zi represents aninteger of 0 to 6, and when zi is 2 or more, a plurality of R¹ and R²may be the same or different form each other, X¹ represents *—CO—O—,*—O—CO—, *—O—CO—O— or *—O— (* represents a bonding site to C(R¹)(R²) orC(Q¹)(Q²)), L¹ represents a single bond or a divalent saturatedhydrocarbon group having 1 to 28 carbon atoms, and —CH₂— included in thesaturated hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—,R³ and R⁴ each independently represent a cyclic hydrocarbon group having3 to 18 carbon atoms which may have a substituent, and —CH₂— included inthe cyclic hydrocarbon group may be replaced by —O—, —S—, —SO₂— or —CO—,and Z⁺ represents an organic cation.
 2. The salt according to claim 1,wherein X¹ represents *—CO—O—, *—O—CO— or *—O—CO—O— (* represents abonding site to C(R¹)(R²) or C(Q¹)(Q²)).
 3. The salt according to claim1, wherein L¹ is a single bond, an alkanediyl group (—CH₂— included inthe alkanediyl group may be replaced by —O— or —CO—) or a group obtainedby combining an alkanediyl group and an alicyclic saturated hydrocarbongroup (—CH₂— included in the alkanediyl group may be replaced by —O— or—CO—, and —CH₂— included in the alicyclic saturated hydrocarbon groupmay be replaced by —O—, —S—, —SO₂— or —CO—).
 4. An acid generatorcomprising the salt according to claim
 1. 5. A resist compositioncomprising the acid generator according to claim 4 and a resin having anacid-labile group.
 6. The resist composition according to claim 5,wherein the resin having an acid-labile group comprises at least oneselected from the group consisting of a structural unit represented byformula (a1-1) and a structural unit represented by formula (a1-2):

wherein, in formula (a1-1) and formula (a1-2), L^(a1) and L^(a2) eachindependently represent —O— or *—O—(CH₂)_(k1)—CO—O—, k1 represents aninteger of 1 to 7, and * represents a bond to —CO—. R^(a4) and R^(a5)each independently represent a hydrogen atom or a methyl group, R^(a6)and R^(a7) each independently represent an alkyl group having 1 to 8carbon atoms, an alicyclic hydrocarbon group having 3 to 18 carbonatoms, or a group obtained by combining these groups, m1 represents aninteger of 0 to 14, n1 represents an integer of 0 to 10, and n1′represents an integer of 0 to
 3. 7. The resist composition according toclaim 5, further comprising a salt generating an acid having an aciditylower than that of an acid generated from the acid generator.
 8. Theresist composition according to claim 5, further comprising a resinincluding a structural unit having a fluorine atom.
 9. A method forproducing a resist pattern, which comprises: (1) a step of applying theresist composition according to claim 5 on a substrate, (2) a step ofdrying the applied composition to form a composition layer, (3) a stepof exposing the composition layer, (4) a step of heating the exposedcomposition layer, and (5) a step of developing the heated compositionlayer.